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New Jersey Scuba Diving

Conservation of Iron & Steel - Part I

As stated in previous section, the preliminary evaluation of an iron artifact will determine the methods by which the artifact is cleaned. Only after an artifact has been evaluated and cleaned can the appropriate conservation measures be taken. The various treatments available for the conservation of iron can be organized into five general categories:

  1. Electrochemical cleaning
    a. Galvanic cleaning
    b. Electrolytic reduction
  2. Alkaline sulfite treatment
  3. Chemical cleaning
  4. Annealing
  5. Water diffusion in alkaline solutions

The corrosion of metal, as explained earlier, is an electrochemical reaction. Electrochemical and electrolytic reduction cleaning processes, therefore, are the most common techniques utilized to halt, stabilize, and even reverse the oxidation of the metal. In the field of conservation it has been the general practice to distinguish between electrochemical and electrolytic cleaning. An electrochemical reaction is based upon the association of two metals occupying different positions on the galvanic or electromotive series of the metals without an externally applied electromotive force ( EMF ); therefore this cleaning process is also known as galvanic cleaning. Electrolytic reduction, also called electrolysis, is an electrochemical reaction maintained by an externally applied EMF or electric current. Basic information on these two processes can be found in Plenderleith ( 1956 ), Plenderleith and Torraca ( 1968 ) and Plenderleith and Werner ( 1971 ). Hamilton ( 1976:30-49 ) and North ( 1987:223-227 ) provide detailed discussions of electrolytic reduction.

Galvanic cleaning is often mentioned as an effective method for conserving shipwreck material. In two frequently cited works on underwater archaeology, it is the only technique recommended ( see Peterson 1969:83-84; Marx 1971:125 ). For marine-recovered iron artifacts which are severely chloride-contaminated, however, galvanic cleaning is not a favorable alternative. It is often not desirable even for metals from terrestrial sites, where chlorides present no real problems.

To be effective, galvanic cleaning requires that a substantial metal core be present in the object being treated. In most circumstances, this process can be recommended only if a few small objects are to be cleaned and if equipment for electrolytic cleaning is not available. Except for limited use, galvanic cleaning is best considered as an obsolete technique. Since it is used in some laboratories, however, it is briefly discussed here. Some of its advantages and its major disadvantages are presented.

Galvanic cleaning involves placing the iron object in a vat and surrounding it with a more active anodic metal, such as zinc or aluminum, and filling the vat with an electrolyte. In this process, nascent hydrogen acts as the reducing agent as it evolves from the surface of the iron. The chlorides are removed, and reduced metal is left by the reaction. In order for galvanic cleaning to be effective, it is necessary to control the electrode potential of the artifact being treated. In galvanic cleaning this is determined by the couple between the anodic metal and the iron and by the electrolyte; once the electrode potential of the artifact has been established, however, it cannot be manipulated.

The simplest method of galvanic cleaning consists of wrapping the object loosely in aluminum foil and placing it in a glass beaker of 10 percent sodium hydroxide, or caustic soda ( NaOH ), or a 10 to 20 percent solution of sodium carbonate, or soda ash ( Na2CO3 ). ( No? Hume [1969:283] suggests using an electrolyte of baking soda ( sodium bicarbonate, NaHCO3 ), but tests at the Texas A&M Conservation Research Laboratory have shown that baking soda electrolytes are not effective in galvanic cleaning. ) the object is left in the caustic solution until the aluminum foil completely oxidizes. The reaction can be speeded up by heating the solution. The object is then rinsed, and the process is repeated until satisfactory results are achieved. Only small, lightly corroded specimens can be treated in this fashion.

The most commonly used method of galvanic cleaning differs from the method above only in that granulated zinc or aluminum granules are used to cover the object and a 10 to 20 percent solution of sodium hydroxide is employed ( Plenderleith and Torraca 1968:241; Plenderleith and Werner 1971:194-197 ). The solution is heated to boiling in a metal pan or heat-resistant glassware, and the level of the solution is maintained with the addition of distilled water. The cleaning continues until the electrolyte is exhausted or the activity of the zinc abates. The process is repeated with fresh or cleaned zinc and fresh caustic soda until all of the materials are reduced and all traces of chlorides have been eliminated. If high levels of chlorides are allowed to remain in the artifact, future outbreaks of corrosion are inevitable.

This process requires facilities to heat the container and an adequate ventilation system, such as a fume hood, to exhaust the caustic vapors. In the reduction process, the caustic solution is exhausted and has to be periodically discarded, and considerable zinc is lost through oxidation. The activity of the remaining zinc is significantly reduced by an accumulated film of oxychloride and carbonate. To be renewed, the zinc must be cleaned with dilute hydrochloric acid solutions, rinsed in distilled water, and then dried ( Plenderleith and Werner 1971:196 ). Alternatively, the zinc can be melted in a ladle under a reducing flame and re-granulated by slowly pouring the molten zinc into water ( Organ 1973:193 ); each time the zinc is reclaimed, slag formation will further reduce the quantity of zinc.

For iron artifacts, or any other metal with extensive chloride corrosion compounds, the galvanic cleaning process is impractical. The artifact is always obscured, so it is not possible for the conservator to observe its progress. Even under ideal conditions, the process requires constant supervision and is messy. The fumes produced are unpleasant and irritating to the skin, eyes, and throat. Furthermore, it is often difficult to provide simultaneously adequate ventilation and adequate heat. Large artifacts, especially those which are chloride-contaminated, require a long processing time and a prohibitive amount of zinc, which has to be continuously cleaned and replenished.

Galvanic cleaning of most metal artifacts should be considered only if equipment for electrolytic reduction is unavailable, and even then, it may be a waste of time for a majority of iron artifacts, especially if they are very large. No? Hume's comment ( 1969:276 ) bears repeating: "Those amateurs who have been told that it is a simple method that can readily be performed on the kitchen stove are advised to forget it."

Electrolytic reduction cleaning is one of the most efficient and effective methods of conserving metal artifacts. Electrolytic units are very cost-effective and simple to set up and maintain. The cleaning process can be selected exclusively for its mechanical cleaning action of the evolved hydrogen, for the metal reduction process or a combination of the two. Efficient electrolytic reduction, however, involves more than simply wiring up artifacts for electrolysis. A knowledge of corrosion processes and electrochemical thermodynamics is essential. The conservator must be familiar with electrode potentials and pH and know how these variables relate to electrode corrosion, passivation, and immunity. These factors are particularly crucial when dealing with chloride-contaminated metals. This is not to say that satisfactory results cannot be obtained by the novice, but rather that knowledge and experience enables the conservator to understand and better control what is going on in the electrolytic cell and to correct adverse conditions.

The essence of the technique involves setting up an electrolytic cell with the artifact to be cleaned as the cathode. An electrolytic cell consists of a compartment or vat with two electrodes, the anode and the cathode, and contains a suitable electricity-conducting solution called the electrolyte. An electric current from an external direct current ( DC ) power supply is applied to cause oxidation and reduction. The anode is the positive terminal of the electrolytic cell, to which electrons, negatively charged ions, or colloidal particles, travel when an electric current is passed through the cell. Oxidation occurs at the anode and oxygen is evolved. The cathode is the negative terminal of an electrolytic cell, to which positively charged metallic ions travel. At the cathode, reduction takes place and hydrogen is evolved. In the reduction process, some of the positively charged metal ions in the compounds on the surface of the artifact are reduced to a metallic state in situ. In addition, chlorides and other anions are drawn from the specimen and migrate toward the positively charged anode by electrolytic attraction.

The chief advantage of electrolytic reduction is that the density of the externally applied electromotive force ( EMF ), or electric current, can be controlled. This control enables the conservator to select a low current density that creates a preselected electrode potential conducive for the consolidation and/or reduction of some mineralized metals. When there is an underlying metal core, it is theoretically possible to reduce enough of the ferrous corrosion compounds back to a metallic state through electrolytic reduction. This will consolidate the corrosion layer while eliminating the chloride components of the compounds. A high current density can be selected so that the evolved hydrogen will mechanically remove any completely oxidized crust.

When using electrolytic reduction cleaning, factors to be considered are the equipment and the experimental variables.

  1. Power Supplies
  2. Terminal Wires and Clips
  3. Anode Material
  4. Chloride Monitoring
  5. Vats

Experimental variables

  1. Types of Electrolytic Setups
  2. Electrolytes
  3. Current Densities
  4. Electrode Potentials

DC Power Supplies

The regulated DC power supply requirements for electrolytic reduction are wide-ranging, and a well-equipped laboratory should have several units of varying current capacities, each of which is capable of continuous operation. Power units fall into four general current ranges and are capable of cleaning any object from the size of a small spike to a large anchor or cannon.

Most small DC power supplies have an output current with less than 0.1 percent ripple. The larger power supplies have 0.5 percent or more ripple. For well-controlled reduction, the low ripple power supplies are recommended; a little ripple, however, is not harmful. The choice of a power supply depends upon the desired current density control, the size of the artifact, and the number of artifacts on any one unit. Current controls and an amperage meter provide a means of determining and adjusting the current as the treatment progresses. During electrolysis, the current increases as the metallic species are reduced and the resistance of both the object and the electrolyte decreases. The current resistance ( IR ) drop in the electrolyte is due to an increase in chloride and other ions. This is the main reason for the current increase; the decrease in the resistance of the object plays only a minor role. Therefore, variable adjustments are necessary if an object is to be electrolytically reduced at a fixed current density or a predetermined electrode potential.

Because of the expense of regulated power supplies it is not surprising that many conservation laboratories build their own power units. Foley ( 1967 ) and Organ ( 1968:291-308 ) give directions on how to build an inexpensive power supply. Alternatively, battery chargers can be employed. Battery chargers, however, are not designed to run continuously for electrolytic cleaning. If they are to be used in electrolysis, it is usually necessary to remove timers, relays, and charging rate devices to make them serviceable. Since an electrolytic cell for cleaning artifacts lacks the resistance of a battery, and the battery chargers generally do not have the necessary internal resistance controls to compensate for it, the chargers run well above their maximum safe operating amperage. Additional resistance must be added to the circuits to keep them from overheating. Variable autotransformers, such as Powerstats, on the input alternating current ( AC ) line and variable rheostats, or line resistors, on the outgoing DC negative terminals serve this purpose well. Anyone with a basic knowledge of electrical circuits can easily alter most direct current battery chargers for electrolytic cleaning of metal artifacts.

Terminal Wires and Clips

For most objects, terminal wires made of U.S. National Electric Code Standard 16 AWG, Separation 2, 300V maximum rating insulated copper wire can be used. This wire is the standard two-ply multistrand wire commonly found on many electrical appliances and is quite flexible and easy to use. One strand of the wire is used for the negative connection, the other for the positive connection; or they can be joined at the terminal ends to make one pole connection if a larger sized wire is required. For larger artifacts that need more current, No. 2 to No. 0 AWG multistrand wire is required. Multistrand copper wire is recommended in all cases because it has a larger current capacity and is more flexible and easier to manipulate than comparably sized solid wire. Before using any wire, one should check the amperage capacity of the wire, or, if in doubt, consult an electrician. A good rule of thumb to follow is that the wire should not heat up during electrolysis; if it does, the wire is not heavy enough.

Steel alligator test and battery clips ( Mueller clips ) are recommended for attaching the terminal leads to the artifact and the anode. Appropriately sized clips on the terminals facilitate setting up and taking down artifacts in electrolysis. These clips come in a variety of shapes and sizes. The size of the clip selected is determined by the current to be used, the size of the artifact, and the placement of attachments. Mueller clips Nos. 25, 27, 48 and 85 are the most useful sizes and should be kept in stock. Steel clips, which are usually are cadmium- or zinc-plated, should be stripped of this plating by a quick bath in a dilute solution of hydrochloric acid before use ( if left too long in the acid, the tempered steel spring is weakened and will break when depressed ). The removal of the cadmium or zinc coating prevents any plating of this metal from the anode clips onto the artifact. For this same reason, copper clips should not be used. Copper clips on the positive terminal, like the exposed copper wire attached to the anode clips, eventually go into anodic dissolution when submerged in the electrolyte and plate onto the cathode. In order to prevent anodic dissolution, any copper wire that is exposed in the electrolyte should be coated with an acrylic, polyvinyl acetate, or silicone rubber.

Anode Material

For electrolytic cleaning of iron, 16-gauge expanded mild steel mesh with half-inch openings is an inexpensive but efficient anode material. This steel mesh is easily cut, relatively flexible, easy to form-fit around the artifact and does not conceal the artifact from view. It also permits free circulation of the electrolyte and will not trap any gases. Mild steel plates, and even sheets cut from mild steel drums, make serviceable and cheap anode material, but their rigidity makes them difficult to form-fit around an artifact. Specially constructed mild steel vats, or even 55-gallon steel drums, can serve both as the electrolytic vat and the anode material. When a form-fitted anode is desired, however, only expanded steel mesh is cheap enough and flexible enough for regular use.

Mild steel anodes are surprisingly durable. As long as an adequate alkaline pH ( minimum of 8.5 ) is maintained at the surface of the mild steel anode, it is less susceptible to chloride corrosion and will even outlast stainless steel. To maintain this level of alkalinity, it may be necessary to circulate the electrolyte. Mild steel anodes are commonly used as the oxygen-hydrogen cell electrodes ( Worth Carlin 1975, personal communication ).

It is claimed that stainless steel makes a superior anode, and it is often recommended because it is relatively inert and seldom needs to be replaced. All stainless steels, however, do not make equally suitable anode material. A stainless steel with a high percentage of chromium and nickel or even titanium must be selected; Type 316 stainless steel, which is composed of 16-18 percent chromium, 10-14 percent nickel, and 2-3 percent molybdenum, is recommended. Only Type 316 stainless steel resists chloride corrosion and is a good alternative to mild steel anodes in an alkaline electrolyte.

The high cost of stainless steel generally restricts its use as anode material for large objects and makes it impractical to cut and form-fit it to clean a single artifact. The most practical way to use stainless steel anodes is in certain electrolytic setup alternatives that allow for a number of artifacts to be treated at one time. These setups will be described below.

As long as the hydroxyl ion concentration in the electrolyte is kept high, mild steel anodes are more efficient than stainless steel anodes. Regardless of the anode material, it is much simpler and more economical to change the electrolyte before the chlorides build up to such an extent that they alter the pH and electrode potential at the anode, destroying the anode's passivity and causing it to go into dissolution. When this happens, the anode has to be replaced.

A wide variety of containers can be used in an electrolytic setup. Many kinds of non-conductive vats of various caustic and acid-resistant plastics, such as polyvinyl chloride ( PVC ), polypropylene ( PP ), and polyethylene ( PE ) are widely used. PVC plastic pipes with sealed ends make excellent vats for long, slim artifacts, such as rifle barrels. Fiber-resistant plastics should be avoided unless it is certain that they are alkali-resistant. Glass containers are also suitable for electrolytic setups, as are wooden vats, or frames lined with sheets of PVC plastic ( care must be taken not to puncture the plastic ).

In addition to non-conducting containers, conducting mild steel vats are frequently used in electrolyte cleaning. The metal vat serves as all or part of the anode and may be substituted as such in any of the electrolytic setups described below. Metal vats also have a distinct advantage over plastic vats in that all stages of the conservation process can be carried out in them. This is especially advantageous for very large pieces, where it is not economically feasible to have different vats for electrolysis, rinsing/dehydration, and wax impregnation.

Mild steel vats can be constructed in various gauges and are surprisingly durable and versatile, even in the lighter gauges. Use a gauge that provides the strength required and does not increase the weight of the setup beyond the laboratory's ability to handle it. A common coffee can, with the can used as the vat and the anode, is a simple and effective container for small artifacts. Mild steel 55-gallon drums, cut lengthwise or in half, make readily available, cheap vats, which can be employed in any of the described setup alternatives, in combination with auxiliary anodes to assure a more even distribution of current. Welded mild steel vats can be constructed cheaply and will last for years. For very large artifacts, such as anchors, a two-piece 5-m long mild steel vat is recommended. This 'T'-shaped vat is constructed of two parts, the stem and the cross, each of which is open at one end. When the parts are joined, the vat is used to clean anchors with auxiliary sheets of expanded mild steel positioned near the top surface of the anchor in order to achieve a better distribution of current. Separated, the two vats can be employed to clean an assortment of large iron artifacts.

When corrosion takes place in a conducting mild steel vat, it will occur at the stress points, such as weld lines and bends in the metal. It is for this reason that North ( 1987:225 ) discourages the use of a mild steel vat as an anode. If a metal vat is not hooked up as the anode, the fact that it will not be anodically passivated affords it some protection; however, any chloride ions present will still eventually corrode the vat. Furthermore, if a mild steel vat completely corrodes in 10 years due to its use as the anode, it can be easily replaced many times and still be more economical than stainless steel or plastic alternatives. The recommendation by North is disregarded by most conservators responsible for treating large iron artifacts from marine sites.

Care must be taken to ensure that metal anode vats remain passive during electrolysis; otherwise, the metal will go into anodic dissolution and create perforations, which are difficult to repair. This is sometimes difficult when using low current density electrolysis in the presence of high levels of Cl- ions; however most of the difficulties can be overcome if a 5 percent sodium hydroxide electrolyte is used until the chloride levels decrease or the current density can be increased to keep the anode passive. This issue will be discussed in more detail later in this section.

Conservators should be aware of some safety issues regarding the use of metal vats as both the container and the anode. Most DC power supplies used in electrolytic cleaning operate in a 6- to 12- or a 24- to 32-volt range and a 0- to 50- or 0- to 200-amperage range, but the actual voltage used during electrolytic cleaning usually does not exceed 6 volts. At this voltage, there is little personal danger in using metal vats. In general, a voltage of less than 32 volts is not hazardous because the IR drop in the human body is such that little or no current would pass through the body. Care should be taken, however, to avoid shorting the two terminals of higher voltage power supplies against each other.

Chloride concentration monitoring of the electrolyte is crucial to the efficiency and success of electrolytic reduction when conserving metal objects recovered from marine environments. Several methods to quantitatively monitor chloride concentration exist. The mercuric nitrate titration method is recommended in this manual due to its simplicity and low cost.

The mercuric nitrate test is a quantitative method used to determine Cl- or NaCl in parts per million in an aqueous solution. It is a quick and simple test to perform and gives accurate and consistent results. The following procedure is a modification of the method outlined by Furman ( 1962:331-332 ).

  1. One automatic 25 ml burette
  2. Two small amber glass bottles with droppers
  3. One 500 ml amber glass bottle
  4. One 250 ml beaker
  5. A magnetic stirrer
  6. Teflon-coated stirring bars

  1. Diphenylcarbazone-bromophenol blue indicator
  2. 0.02N mercuric nitrate solution
  3. Sulfuric acid

Transfer the blue indicator and the sulfuric acid to the amber dropper bottles. The mercuric nitrate should be stored in the amber glass bottle for refilling the burette.

  1. Take a 20 ml sample of electrolyte or solution to be tested, and place it in the glass beaker.
  2. Place the beaker on the magnetic stirrer and put a Teflon stirring bar in the beaker.
  3. Adjust the stirrer until the liquid is in a steady swirl.
  4. Add five drops of diphenylcarbazone-bromophenol blue indicator. This will change the color of the solution to blue.
  5. Add drops of sulfuric acid ( usually 18N for sodium hydroxide electrolytes, 9N for sodium carbonate electrolytes, or 4.5N for water solutions ) to the solution until an acid end point is reached. The acid end point is indicated by a color change from blue to clear. ( The amount of sulfuric acid does not need to be measured as it only acidifies the sample for the next step. )
  6. Titrate 0.02N mercuric nitrate, drop by drop, from the automatic burette into the beaker until the solution reaches a violet end point. The color changes gradually from clear to violet. Near the end point, each drop will show a flash of color. Continue until a single drops swirls into a single even violet color through out the solution. Note: the sensitivity of the titration can be increased by using a smaller normality solution or decreased by using a larger normality solution of mercuric nitrate.
  7. Note the amount of mercuric nitrate titrated to reach the end point.

The concentration of chloride or sodium chloride in parts per million is calculated by the following formulas:

T x N x 0.03545 x 1,000,000
= T x N x 1772.5 = ppm Cl-
T x N x 0.05846 x 1,000,000
= T x N x 2923 = ppm NaCl

T = amount of mercuric nitrate titrated
N = normality of mercuric nitrate

In order to facilitate the calculation of chloride concentrations, a conversion table can be established using the formulas above:

Amount of Mercuric
Nitrate Titrated ( ml )
ppm Cl- ppm NaCl
0.1 3.5 5.8
0.2 7.0 11.7
0.3 10.6 17.5
0.4 14.0 23.4
1.0 35.0 58.5
10.0 350.0 585.0
etc. etc. etc.

The mercuric nitrate test gives the total amount of Cl- or NaCl in the electrolyte. Unused electrolyte solution, however, will already contain a certain amount of chlorides. In order to determine the amount of chlorides expelled from the artifact, the amount of chlorides present in an unused sample of the electrolyte must be determined. This provides a 'blank' which is subtracted from the amount of chlorides present in a sample taken from the electrolytic bath. For example, if a sample taken from an active electrolytic bath contains 24.5 ppm of Cl- while an unused sample of the same electrolyte contains 17.5 ppm, the amount of chlorides in the electrolytic bath that have been expelled from the artifact is 7.0 ppm.

Comments on the Mercuric Nitrate Test

Throughout this entire process, the glassware must be kept clean and uncontaminated. To prevent cross contamination, a clean beaker and stirring rod should be used for each electrolyte sample, or these items should be washed thoroughly and rinsed with de-ionized water between each sample. Purple mercuric nitrate stains can be removed from the stirring rods by immersing them in dilute solution of nitric acid.

Two notes should be added with regard to the chloride testing procedure. First, the diphenylcarbazone-bromophenol end point is to some degree subjective, but most individuals are consistent about their end point. Therefore, the most reliable and consistent results are obtained when only one individual is responsible for monitoring the electrolyte. To further assure the consistency of chloride monitoring, the reagents should be tested weekly against a known sodium chloride solution.

All of the chemicals in the concentrations required for the chloride test can be purchased from a chemical supply house. Chemical costs can be considerably decreased, however, if the chemicals are mixed in the lab as follows:

During electrolytic cleaning, the chloride level should be calculated and recorded at least once a week. These calculations can be used to make a graph that visually depicts at a glance the progress of chloride removal from an artifact. This will save much valuable time and enable the conservator to determine when all detectable soluble chlorides have been removed from the object, as well as when to change a chloride-contaminated electrolyte. Systematic chloride monitoring assures that the artifact will remain in electrolysis for the least amount of time necessary. Chloride monitoring cannot, however, be used to determine the efficiency of the reduction of the iron compounds. This can only be confirmed with analytical tests on samples taken from the artifact before and after treatment.

diffusion of chlorides into solution during electrolysis
Graph depicting the diffusion of chlorides into solution during electrolysis.

The graph in Figure 10A.1 presents the progress of a typical iron artifact recovered from a marine environment. It clearly depicts the high initial rise in chlorides released from the artifact and the subsequent decrease as the electrolyte is periodically changed. Drops in the graph to the zero line represent electrolyte changes. The two-week gap in the graph in November indicates when the artifact was taken out of electrolysis in order to mechanically clean the remaining encrustation and loose corrosion products. Occasionally, a drop from a previous high is seen on some chloride graphs, especially when the chloride level is high. This may be caused by chlorides reacting with corrosion products from the anode, chlorate formation, or the actual liberation of chlorine which causes the chlorides to be undetectable by taking them out of solution. Electrolysis is continued until the chloride concentration levels off for several days and does not increase above that present in a 'blank' of the electrolyte.

Conservation of Iron & Steel - Part II

  1. The size and condition
    of the specimens
  2. The amount of artifacts
    to be processed
  3. The number of available regulated direct current power supplies
  4. The current capacities of the power supply units
  5. The number, size and
    nature of the vats

electrolytic setup
Figure 10B.1

The most commonly used electrolytic setup involves connecting multiple artifacts to a single power supply. Regardless of how it is configured, Type 3 electrolytic setups ( Figure 10B.1 C-D ) are the least desirable from the standpoint of control, but they have the advantage of processing a number of objects at one time in one vat on a single power supply. In one configuration ( Figure 10B.1 C ), each piece is individually connected to the negative terminal of a single power supply. The artifacts share common anode sheets placed above and below the specimens. An alternative variation of this setup has a common bottom anode and individual top form-fitted anodes to assure a more even distribution of the current to each artifact.

Table 9.1

Electromotive Series of the Metals of Antiquity: Standard Reduction Potentials in Salt Solutions of Normal Ionic Activity at 20°C, pH 0.

Noble End
( Cathodic )
( +1 aurous, +3 auric )
Au+3 ( + 3e- )<< >> Au +1.50
( +1 )
Ag+ + e- << >> Ag +0.799
( +1 cuprous )
Cu++ e-<< >> Cu +0.552
( +2 cupric )
Cu+2+ 2e- << >> Cu +0.337
( +1 )
2 H++ 2e-<< >> H2 0.00 0.00
( +2 plumbous, +4 plumbic )
Pb+2 +2e- << >> Pb -0.126
( +2 stannous, +4 stannic )
Sn+2 + 2e- << >> Sn -0.136
( +2 ferrous )
Fe+2 + 2e- << >> Fe -0.440 -0.409
( +3 ferric )
Fe+3 + 3e- << >> Fe -0.036
( +2 )
Zn+2 + 2e-<< >> Zn -0.0763
Base End
( Anodic )

* Electrode potentials in left column are from Evans ( 1963:end papers ); potentials in the right column are from Hunsberger ( 1974:D120-125 ).

electromotive series

The electromotive series in Table 9.1 (above) indicates that the reduction reaction of ferrous ions, Fe+2 Fe - 2 e, occurs at -0.409 volts to -0.440 volts at a pH of 0. The reduction potential increases -0.029 volts for each pH increase. The reduction of ferric ions, Fe+3 Fe - 3e, occurs at -0.036 volts and increases -0.019 volts per pH increase. The hydrogen discharge potential, 2 H+ H2 - 2e, occurs at a voltage potential of 0 and increases -0.058 volts per unit of pH increase. The reduction potential of ferrous, ferric, and hydrogen ions at different pHs at a standard temperature of 20°C are graphically presented in Figure 10B.3. This graph makes it possible to determine the theoretical electrode potential voltage necessary for reduction of ferrous corrosion products in an electrolyte of known pH and ion content. It is thermodynamically impossible to reduce ferric oxide and other ferric iron corrosion compounds in an aqueous solution; this point is also graphically depicted in Figure 10B.3. The electrode potential for the reduction of ferric corrosion products is well out of the range possible for electrolytic reduction in an aqueous alkaline electrolyte with an external EMF.

reduction potentials of ferric, ferrous, and hydrogen ions

reduction potentials

reduction electrode potential

The electrode potential at the surface of the cathode is a critical factor in the reduction of corrosion compounds during iron electrolysis. As the hydrogen discharge potential of the cell is reached, hydrogen ions are formed which reduce adjacent ferrous compounds. ( At more negative electrode potentials, molecular hydrogen will form so rapidly that the molecules will combine with each other and evolve as hydrogen gas; this evolution of hydrogen acts as a mechanical cleaning agent that physically removes any unconsolidated corrosion layers. ) the theoretical point at which the maximum reduction and/or consolidation of the ferrous corrosion compounds is achieved is at the intersection of the hydrogen discharge line and the ferrous ion reduction line or immediately to the left of this intersection ( see Figure 10B.3 ). Using the formula Fe+2 + 2e Fe and substituting values for the Fe+2 reduction potential and the correction for pH [( -0.409 )( -0.029 )( pH )], this intersection appears at a pH of 14.1 and an electrode potential of -0.82.

metal reduction

metal reduction
Figures 10B.6 and 10B.7

Reducing Electrolysis Time

The stage at which the chloride ( Cl- ) level in the electrolyte is reduced to below 50 to 100 ppm requires the greatest amount of electrolytic cleaning time. Below 100 ppm Cl-, the artifact is assumed to be in the final stages of cleaning. There are at least two explanations for the long amount of time required to remove chlorides during electrolysis: ( 1 ) the electrolysis is carried out at high current densities which have a tendency to repress Cl- migration in preference for H2 evolution, ( 2 ) the Cl- concentration in the electrolysis is governed by the Donnan equilibrium theory.

Regardless of whether tannic or phosphoric acid is used, it is highly recommended that a sealant, such as microcrystalline wax, be applied over the film formed on the object, the wax will provide a vapor barrier, which the film does not, and will also contribute some strength to corrosion layers on the metal.

Donny L. Hamilton
1998. Methods of Conserving Underwater Archaeological Material Culture. Conservation Files: ANTH 605, Conservation of Cultural Resources I. Nautical Archaeology Program, Texas A&M University, World Wide Web, http://nautarch.tamu.edu/class/ANTH605/.

Copyright 2000 Donny L. Hamilton, Conservation Research Laboratory, Texas A&M University

Copyright © 1996-2016 Rich Galiano
unless otherwise noted

since 2016-09-11


Crude Oil Insights Crude Price Outlook, Uncategorized Crude Oil Price Update- WTI Falls on Weak US Economic Data; Brent Rises

Oil futures fell by the biggest weekly amount in a month amidst news that the US Unemployment rate increased to its highest level this year. WTI crude futures fell by 0.18 percent to USD $ 100.22 a barrel.

The US Labour Department stated that the number of payrolls increased by only 54,000 in May, the smallest increase this year. The unemployment rate from 9 to 9.1 percent. For the first time in almost seven months, factories in the US cut down on the number of people employed by 5000, whereas the number of new jobs added in the retail, leisure and state and local governments also decreased in May. Further compounding this pessimistic outlook was a revised report from the US Commerce Department, which stated that the US economic growth in the first quarter of this year was a meager 1.8 percent per annum, down from the growth rate of 3.1 percent per annum in the previous quarter. This news has increased speculation about a decreased demand of oil in the US during the summer season, which has led to a fall in the price of oil futures.

Meanwhile, Brent crude futures increased by 0.26 percent to USD $ 115.84 a barrel. The Euro appreciated against the Dollar, which has resulted in commodities priced in the Greenback, such as Brent futures, appear more attractive to European investors. Thus, this increased demand for Brent futures led to its price hike.

Author: Usman


Wednesday, July 18, 2012

“If You Got a Business, You Didn’t Build That”

Those are Obama’s very telling words and why he is a dangerous leader. This is exactly how a socialist or even communist would think – that government intervention is the solution to everything including innovation and all the products developed in our country. This is why Obama and the left want to redistribute wealth and make sure every American citizen is dependent on the government to survive – they actually believe this leads to economic success. They believe spending is investment and therefore, a dollar spent on welfare creates more than a dollar of wealth in GDP.

The below study will show exactly why government intervention hinders innovation and product development because it constrains the private sector with rules, regulation, mandates, and other anti-business legislation.

According to a Patent Board study (study done by the U.S. Government) from 2003 to 2007, the U.S. government accounted for 1% of all patents developed internally, and 2% of all patents developed in cooperation with private industry through federal funding. The U.S. government is most active in patents owned and shared in fields of Biotechnology (13%), Defense and Aerospace (8%), and Semiconductors (2%). In these fields, government developed patents are rarely cited, but sponsored patents with private industry do have some significant credence because they are widely cited. The bottom line is that federal government has shown little innovation with exception of the fields in Biotechnology, Defense, and Semiconductors where their private sector funding patents have shown some broad success. However, other than that, the government has shown little overall innovation in other high tech, healthcare, energy, education, or financial fields.

This past year government discretionary spending accounted for about 9% of GDP (total federal spending accounted for about 25% of GDP). Yet, the government only account for 2% of the innovation (patents). This not only illustrates how abysmal the federal government is when it comes to innovation and research and development, but shows the waste in government spending. If this is not bad enough, government innovation numbers are much worse when we consider local and state government discretionary spending versus GDP. Locality and state governments offer a very few patents – about 0.1% of the total. Therefore, total government discretionary spending (Local, State, and Federal) accounts for better than one eighth of our national GDP, but only a little more than 2% of the total patents or innovation. What’s worse, total government spending (Local, State, and Federal) accounts for over 40% of total GDP in the country. Hence, the private sector accounts for less than 60% of the GDP, but 98% of the innovation (99%, if we include the 1% of the innovation that is done jointly between the private and government sectors). And the private sector accomplishes this despite government rules, regulations, mandates and other anti-business policies that work to restrict innovation.

According to the above analysis, Obama was right when he said NASA generated a lot of innovation (8% of the patents with even a greater percentage of significant patents that were widely cited). This is good considering government spending is only 6% of GDP on Defense and Aerospace related fields. But remember Defense and Aerospace are the fields that Obama, and progressives alike, want to significantly cut funding. Obama has already killed our space program. Hence, it makes little sense he would even point out the innovations made in the aerospace and defense sector since he is obviously not a proponent for their existence.

Obama also pointed to the public educational system as helping many American citizens. Sure, many of us may point to a teacher that played a prominent role in our success. But the dropout rate across the country is 25% - so our public schools are failing many young people. And the unemployment rate of over 70% for recent college grads is not encouraging news for the public school system either.

To summarize, private sector's products are all around us -- food, shelter, clothing, automobiles, home appliances, entertainment, for example. The public sector's products include defense, the justice system, roads and highways, public schools, income redistribution (welfare), laws, and regulations.

Many of the government sector's outputs are more like anti-products than products. Regulations stifle innovation, decrease productivity, increase costs, and generally drive people crazy. Rather than wealth creation, regulations result in wealth prevention.

“Government innovation across multiple Administrations has generally focused on learning from private sector processes that can apply to support functions like technology, financial management, and HR.” said one government study on innovation. In other words, the government follows in the private sector’s footsteps when it comes to innovation.

  1. >>”This is exactly how a socialist or even communist would think...”

    That’s exactly right. Good post and good comparison of gov’t vs. private sector innovation.

  2. I do not like calling anyone a communist without good reason. I am starting to get a bit bitter that this guy is most likely to win in November. I will keep the hope that the polls change in the next 15 weeks.

  3. Yes, we'd better hope so.

    I have a new post, btw. I'm having trouble getting inspired lately. It gives me renewed respect for your ability to post as often as you do.


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Some parties choose to avoid divorce and opt instead for legal separation. Based on my experience as an attorney, most parties who decide to proceed with a legal legal separation shutterstock_149341619separation rather than a divorce do so for religious reasons, potential health insurance continuation, the existence of a very long-term marriage or hope of reconciliation or a combination of these reasons. Sometimes parties may remain married, but legally separated, in an effort to meet tenure vesting requirements for Social Security or military pensions.

Unlike divorce, a legal separation does not terminate the marriage, but allows you to live separately and independently.  Like a divorce, a Judgment of Legal Separation makes provisions for legal custody and physical placement, child support, maintenance, and property division, as is applicable to the facts and circumstances of each case. A Judgment of Legal Separation must provide that if a reconciliation occurs at anytime after the Judgment, the parties may apply for a revocation of the Judgment.  Upon application for revocation of the Judgment, the court shall make such orders as may be just and reasonable, Wis. Stats. Sec. 767.35(4).   Bartz v. Bartz, 153 Wis.2d 756 (Ct. App. 1989)

In Wisconsin, by stipulation of both parties or on motion of either party, not earlier than one year after entry of the Judgment of Legal Separation, the court shall convert the Judgment of Legal Separation to a Judgment of Divorce.

Consult a top-rated Wisconsin family law or divorce lawyer to discuss your legal options relative to separation and divorce. Don’t assume that legal separation is in your best interests without weighing the benefits and detriments of both legal separation and divorce.


Much of what we do as Technology Education teachers involves a variety of content outside of our core subject (primarily science and math). I try to incorporate a lot of math into my classroom activities whether it’s in the form of measurement, RPM calculations for machinery, dimensioning in my CAD classes, and of course laying out print designs in desktop publishing. The latter is an activity we are currently wrapping up.

Our first graphic design project of the year didn’t really involve much in the way of layout or understanding image/print resolution. However, their last project required that they develop an accurate full size print layout of their project so that they are able to send the job to our color printer. Their project was to design and create a mock credit card (both front and back). All elements of the card were to be created by them (the shape of the card, the lettering, the card type logo, the swipe bar, etc). Before the project began, we discussed how images vary in their resolution (expressed in PPI, or pixels per inch) depending on their use.

First we calculated how to figure out how many pixels are in an image given it’s pixel dimensions (simply take the width x the height). I told them that this is ALL the more pixels a particular image has, and there can be no more than that. This is where camera’s mega pixel ratings come from (1500px x 2000px would be a 3mp camera).

I stressed that most images on the web are low resolution (most commonly 72ppi), and are not suitable for printing. We created a mock high resolution document within Photoshop (ideally not the best page layout program, but it’s what we have). We then took sample images off the internet and placed them into the project window (set at 250ppi). The students observed what happens to the pixels at various resolutions (the image appears to shrink drastically because the number of pixels in an image is constant, the resolution dictates how many of them are in a given inch). We basically broke it down into steps, like this:

Take a 400px x 400px image. That image has 1600 pixels TOTAL (multiply the dimensions). At 72PPI, there are 72 of those 1600 pixels in every inch. At 250PPI, there are 250 of those 1600 pixels in every image. In the latter example, there are more of the 1600 used in every inch, thus the image appears smaller (on screen) than it’s 72ppi counterpart.

I then set up a scenario to calculate appropriate image sizes given a specific resolution as well as a physical print dimension (in inches). We ran through a scenario like this:

You set up project to be printed at 5″x3″ and 250PPI. You need to find an image that will fit that appropriate space at that resolution, and you need this dimension in pixels. So, what they need to do is some basic math:

250 Pixels Per Inch, and the image needs to fit 5″ x 3″. Students must multiply their resolution (250) by each physical dimension (5 and 3) to get the appropriate pixel dimensions which turns out to be
1250px X 750px.

Desktop publishing is both visual based as well as mathematically based. Students need to understand concepts of image resolution, display resolution vs. print resolution, margins, kerning, leading, etc to fully have all the tools to be a successful designer.

This is simply one example of how I try to keep my instruction interdisciplinary, but in reality it’s almost a daily occurrence . From the wood shop to the graphics lab, I’m always incorporating some cross-curriculum content within my lessons. It’s key not only for my subject area’s survival within school districts (as districts begin cutting “elective” classes), but to also help our students see their education as not subject based, but rather content based.


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German to English Translation-Economic & Business Articles

Ladies and Gentlemen,

we seek native English speakers, to translate German language economic and business articles into English.

How does it work?

- The project will start asap.

- In order to get started, I suggest to do an initial TRIAL PROJECT for the duration of 1 week (5 working days/7 days)

- During the trial project I will provide you each working day (Monday - Friday, except public and other local holidays) with 5 (five) German language business/economic articles.

- Once we have started the full project, I would like to provide you with 10 to 20 articles per working day (depending on price, speed, reliability and quality)

- Each article will average 200-300 German language words.

- IMPORTANT: The timeliness of the translation is highly important. I need to know from you, when you are available to do the work, i.e. when you can do the translation? Best, if each working day you are available at the same time in order for us to develop a rhythm method. My suggestion is, that I will provide you with the 5 articles either in the morning (e.g. at 10:00 am) or in the afternoon (e.g. at 4:00 pm) Vienna time (CEST). [CEST (Central European Summer Time, MEZ, UTC + 2 hours, i.e. Vienna, Berlin, Paris, Rome)]

- After I have provided you with the articles, you should be able to translate the articles asap, but not later than within a specified amount of time. (2 hours for 5 articles, accordingly more time for more articles)

- During the trial period you simply need to return the translated articles individually in plain text format (Word Notepad, format .txt) by email.

- Once we have started the full project, you need to make yourself familiar with our CMS. Basically speaking, you need to copy/paste the translated articles into a field and publish the articles directly. Since the CMS work involves additional but simple steps, I will pay a small additional fee to do this. I will provide you on time with login details and detailed instructions, how to use it. (Don't worry, it is fairly simple and self explanatory.)

- IMPORTANT: 1.) Please provide me with your price per English word. 2.) Also provide me with a price per article, if the CMS work takes around 3 minutes per article.

Additional Information:

- This is a long term project and therefore we seek to establish long term relations.

- A background in Economics or Business Administration is required.

- I will pay your fee depending on the amount of English language words. We pay via PayPal (or wire transfer within the EU) every Monday (for all articles submitted in the previous week)

- The articles deal with Austrian business/economic issues. Therefore - during the course of the project - you need to familiarize yourself with certain Austrian terminology, abbreviations, institutions and companies..

- Do not apply if you are not a native English speaker.

- Do not apply if you are not an experienced translator with economic/business background.

- A Skype account for our communication would be very useful.

- All rights to the written articles are transferred to us. We will own the full copyright once we have received the articles from you.

- You may not reuse the articles in any way, therefore they are not permitted to be distributed to other people and organizations.

- All Articles must be translated and written by you in your own words without any grammatical mistakes. You may not outsource the work to other people.

- Please type this in your private message to me... "Ich werde die Übersetzungen schnell, sorgfältig und professionell erledigen!" so I know you read and understand the requirements.

- Please translate the attached sample article (Sample Article 226 German [url removed, login to view]) to prove your quality.

- Please submit your CV (including picture, age, time availability per working day (see above), amount of articles you can handle) together with the quote.

Do not hesitate to contact us for further questions.

Thank you and we look forward to hearing from you.

Skills: Translation

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About the Employer:
( 1 review ) Vienna, Austria

Project ID: #788651


As the name suggests, Mexican Terragon originates from Mexico, where it has been used for centuries by medicine men as a healing herb, and is delicious food flavoring for everyday folks like you and me.

Through the ages, its distinct liquorice-like taste has earned it nicknames like Sweet Mace, Mexican Mint Marigold, Pericon and Yerba Anise, although it’s scientific name is Tagetes lucida.

However, one of the plant’s most famous uses to date has to be as a lucid dreaming aid, which starts by producing improved awareness and slight visions during the waking state, which then translated into an altered dream state that involves the experience of fantastic imagery. Read on for more on this lesser known lucid dreaming herb and how you can use it.

History of mexican terragon

This ancient herb, which has the appearance of a marigold with bright yellow petals and vibrant green leaves, can be traced back all the way to the Aztec civilisation, where it was used as a sedative to dull the senses of sacrificial victims prior to the ceremony. Apart from its ties to this gruesome period in history, this herb has continued to be a source of healing and is one of the most widely used holistic remedies and spices in the Latin American region and beyond.

And Native American shamans have relied on it for centuries to experience vivid dreams and visions or to connect to the ‘other world’.

Mexican terragon uses

Most people use Mexican Terragon as a spice or flavouring for a variety of dishes, from eggs to meat and even chocolate. Others prefer to use it as incense, believing that it’ll cleanse their space of evil spirits and the like.

The plant also contains medicinal properties and through the ages has been used in Mexican cultures to treat ailments such as colds and flus, sleep disorders, rheumatism, as well as stomach aches and indigestion. For best results, add it towards the end of the cooking process, so that you can get the most out of the natural flavour and experience some of its healing properties as well.

Lucid dreamers, on the other hand, use Mexican Terragon to complement other dreaming herbs like Ayahuasca, a combination which could help to eliminate the nausea and other side effects that come with a powerful trip, while also increasing your ability to recall the dreams afterwards.

In traditional Mexican culture, medicine men and women waft it over a person’s body to cleanse the spirit, heal traumas and even to perform soul retrieving ceremonies, and of course we know that it works great when wanting to experience symbolic and even visually rich dreams.

Mexican terragon dosage for lucid dreams

The active ingredients in Mexican Terragon are best enjoyed while the leaves are still fresh, because the effects tend to dissipate when it’s dry. Depending on your preferences, you can either smoke the plant, or take it orally as a tea or spice. If you’ll be smoking it then keep in mind that Mexican Terragon tastes great when smoked alone, but can be dreadful when combined with tobacco.

In preparing it, you can use the entire plant, including the stems, leaves and flower, as they all contain compounds that produce oneirogenic, anti-viral and healing medicinal benefits. But you can also use this as a tincture or essential oil, both of which have been reported to work incredibly well as aphrodisiac and sleeping aids.

It is also recommended to eat something before or after taking this herb, so as to help it to get into the blood stream faster. A popular method of preparing it would be to combine it with some grain alcohol and flavour it with a natural sugar, which really brings out that liquorice taste. In terms of the actual dosage, twenty grams should get you the desired result, although to it’s perfectly safe to add a little more to the dosage if you have a higher tolerance.

Regardless of how you choose to consume it, just be sure to take it while it’s still fresh, as storing it will only serve to weaken it over time. Also, finding fresh Terragon can be difficult so it’s recommended that you try growing it on your own so that you always have a fresh supply available to use.

How to grow your own mexican terragon

Mexican Terragon is a perennial plant which can grow to a height of up to 30 inches when exposed to consistent sunlight. Also, it grows best in well-drained soil, and although drought resistant, requires regular watering in order to thrive, especially in the beginning. You’ll start to notice blooming in the early spring, but it’ll only come into full potential during the fall season, where you can harvest it to your heart’s content to experience potent effects.

The best part about growing your own Mexican Terragon is that it’s really easy to grow because it proliferates on its own, and the leaves start growing roots as soon as they touch the ground. They also germinate fast, so you should be able to transplant them within two weeks of planting.

Those who have burned the dried leaves of this herb report experiencing a state of lucidity which amplifies day-to-day consciousness, produces a tingling warm sensation in the body, a slower passage of time, and an overall feeling well-being, while the dream state experienced while on this herb may include unusual visuals and the ability to completely recall the smallest detail from those dreams.

It is also possible to experience an altered and vivid dream state while on Mexican Terragon, granted that you consume it fresh and take it in the right quantities. It may not be as strong as other oneirogens, but it still produces memorable dreams that may even hold meaning for the dreamer. Plus, its use and effects are supported by use in ancient rituals that span centuries, so it’s definitely worth a try.

Side Effects

Mexican Terragon is quite a delicate and tame herb and has no own wide effects or contraindications. However, it is prohibited for use when pregnant or lactating, as with most potent herbs.

While it may not be the most powerful or popular dream herb out there, Mexican Terragon can hold its own weight, with the ability to produce completely detailed and vivid dreams while improving dream recall.

It is especially recommended for novice lucid dreamers who might need something mild to introduce them to the practice, while experienced reamers will appreciate the increased awareness and calm state that it promotes.

Just remember to flavour it with some honey if taken orally and consume it fresh for best results. Growing your own is a breeze too, as this hassle-free plant only requires moist soil, sunlight, some watering and very little maintenance over time. That said take caution to stay within the recommended dosage and you you’ll be enjoying some of the most marvellous states you can ever imagine.

Grab some of your own Mexican terragon here and read up about other lucid dreaming herbs that you can use or grow in your own home! Also, have a look at the lucid dreaming bootcamp if you want to get some fast results!


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