Understanding Corrosion

There are two primary sources of corrosion:

1.  Oxidation: Oxygen or chlorine combines with a metallic receptor to generate an oxide film. Since the volume of the oxide film is greater than the original metal receptor, this process causes paint coatings to uplift and fail.

2.  Electrolysis: If two dissimilar metals are connected by a conducting film, an electrical potential is created between the two metals. The metal with the higher electrical potential is the cathode, and it loses electrons to the other metal, which is the anode.

TC-11 effectively addresses both types of corrosion.

Oxidation Corrosion

Metals have an oxidation potential which is the tendency to combine with an oxidizer such as oxygen or chlorine and to release heat.  Metals also have the tendency to transform form the refined state to the oxidized, or passivated state. This is the driving force behind oxidation corrosion.

Some metals, such as iron, have a high oxidation potentials which is why iron  rusts so quickly. Sodium has such a high oxidation potential that it bursts into flame at room temperatures when it comes into contact with oxygen.

Other metals, such as chromium, have very low oxidation potentials, which is why chromium rusts so slowly, if at all. Gold, palladium, platinum, and some other noble metals have oxidation potentials that are so low that they will not oxidize at ambient temperatures and pressures.

Oxidation corrosion is controlled by placing a film that is not permeable to oxygen between the oxygen in the atmosphere and the metal. This is referred to as a primer coat.

Oxidation corrosion can take place even if the surface is underwater. The trace concentration of oxygen in the water is enough to support a rapid corrosion rate.

Electrolytic Corrosion

Electrical potential is similar to oxidation potential. If two dissimilar metals are “connected” by a solution that has ions (or free electrons) in it, an electrical potential (or difference) exists between the two metals. The metal with the higher potential will give up electrons and the metal will the lower potential will gain electrons.  In the process of giving up electrons, the molecules of one metal actually migrate to the other metal. You end up with cavities in one metal (the cathode) and deposits on the other metal (the anode). This comes in very handy if you are trying to anodize aluminum, but it creates severe corrosion problems in most situations.

Electrolytic corrosion is corrosion that is caused by the difference in electrochemical potential between dissimilar metals that are connected by a conducting solution Since all different metals have different electrochemical potentials, whenever two different metals are connected by a conducting fluid such as tap water, rain water, or salt water, corrosion will take place at a rate that is a function of the voltage difference between the two metals. This can be 1.5 volts or more, so the damage can be quite extensive. The metal with the higher electrochemical potential – the cathode – ends up with pits and cavities, and the metal with the lower electrochemical potential – the anode – ends up with deposits.

Electrical potential is the same as electrochemical potential from a functional perspective, but the terms cannot be used interchangeably. Electrical potential is created my mechanical means, usually by moving a piece of iron through a magnetic field. If the iron core is rotating, the device is referred to as a generator if it produces a direct current and an alternator is it produces an alternating current. Batteries are examples of electrochemical devices.

If an insulator s inserted between dissimilar metals, no corrosion takes place. Distilled water does not conduct electricity. The impurities, or dissolved solids, in water conduct the electricity, not the water itself. Distilled water can be used to wash high tension lines without electrocuting the equipment  operators.

If the two metals are actually touching, the metals are at the same electrochemical potential and no flow of electrons takes place. This is why it is possible to use a copper washer on a steel bolt and not to have electrolytic corrosion problems as long as the parts stay dry.

Hydrocarbons do not conduct electricity. It is possible to use oil as an insulator for transformers that operate with thousands of volts of electrical potential with complete safety.

TC-11 is a pure hydrocarbon. This means that it is an excellent insulator.

If a film of TC-11 is in place between the dissimilar metals, no electrons will flow between the two metals. This is true even if the two metals are exposed to salt water, rain water, or tap water.

Sacrificial Anodes

Sacrificial [modal id=”6896″]anodes[/modal] should be called sacrificial cathodes, since they are giving up electrons, not gaining them. We will refer to them as sacrificial metals for the sake of clarity.

Zinc is the most common sacrificial metal because it has the lowest electrochemical potential of any commonly available metal.

The theory of using sacrificial metals is that it is better to have a piece of replaceable metal that is intended to lose electrons in order to prevent the rest of the piece of equipment from losing electrons. Typically the sacrificial metal is bolted to the piece of equipment being protected, and it is replaced on a regular basis.

A common mistake is to paint a piece of sacrificial metal. This is a bad idea, since the paint acts as an insulator and it isolates the sacrificial metal from the conducting fluid and it eliminates the protection provided by the sacrificial metal.

Another common mistake is not cleaning the sacrificial metal on a regular basis. Marine growth and dirt can adhere to the surface of the sacrificial metal, and eventually the sacrificial metal is insulated from the conducting fluid and it stops providing corrosion protection.

Sacrificial zincs should always have a metallic appearance. If they are painted, dirty, or encrusted, they are not functioning properly. It is a good idea to rough up the surface of a sacrificial zinc on a routine basis in order to keep if operating at peak effectiveness. It is much better to replace a lot of sacrificial zincs than it is  to replace a single component such as a prop shaft.

Insulators

An insulator is a material that does not conduct electricity. Mica, asbestos, plastic, paint,  rubber, oil, and hydrocarbons are good examples of insulators. TC-11 is an excellent insulator.

This is because the outer orbital shells of the atoms that make up the molecules are “full”. The molecules do not want to give up or lose electrons.

Metals, on the other hand, have outer shells that give up or gain electrons very easily, which is the reason that they are poor insulators and excellent conductors.

Ionized particles are particles that have an electrical charge. The charge can be either negative or positive.

If ionized particles are present in an insulating solution, electrons will drift from the  surface with the higher electrical potential to the surface with the lower electrical potential. This is why non-distilled water is such a good conductor. It is not the water that is conducting the electricity, it is the ionized particles that are suspended in the water. Distilled water is an insulator. Although the individual electrons move relatively slowly, the electrical effect moves at the speed of light.

TC-11 is a pure hydrocarbon, so it is an excellent insulator. An added benefit of TC-11 is that it is highly mobile, i.e. it penetrates in microscopic spaces such as the spaces between the male and female threads of a threaded connector.

If two pieces of metal are actually touching, there is not a space for the TC-11 to penetrate into. From a molecular standpoint the space is “taken”. This means that TC-11 allows metal contacts to conduct electricity at the same time that it protects the contacts from corrosion.

Oxidizing and Reducing Films

A reducing hydrocarbon film is a film that has and excess of hydrogen and carbon molecules available at the metal surface. A reducing film is the opposite of an oxidizing film. An oxidizing film is corrosive. A reducing film is non-corrosive.

Unless a reducing hydrocarbon film is maintained between any piece of refined non-noble metal and the oxygen in the atmosphere, the  metal will eventually  return to its natural oxidized state.

In their natural state, most metals are in the form of oxides: bauxite (white dirt) for aluminum and laterite (red dirt) for iron. The iron refining process removes the oxygen from the metal by raising the temperature of the oxidized ore in a reducing, or hydrocarbon rich atmosphere. The aluminum refining process consists of inducing an electrical current into the ore.  When the aluminum melts, the oxygen molecules are separated from the aluminum molecules.

Induced Current Protection

Induced current devices measure the electrical potential of two dissimilar metals connected by a conducting fluid and they add enough of a voltage to the metal with the lower electrical potential to stop the flow of electrons from the metal with the higher electrical potential.

These devices have been used for decades by the navies of the world to prevent electrolytic corrosion on ships that are in storage. They are also effective at preventing electrolytic corrosion on buried pipelines.

These devices are not effective on vehicles because there is not a conducting fluid that connects the dissimilar metals.

Induced current protection devices are recommended for boats that are stored in the water. If thee boat is stored on dry land, there is no point in using this type of device. Induced current devices do not protect metal parts that are not touched by the conducting fluid. This means that all of the dry parts on a boat are not protected by an induced current device.

TC-11 complements induced current protection systems. These devices do not address corrosion generated by oxidation, and TC-11 does. In addition, TC-11 protects the metal components that are not exposed to the conducting fluid.

The Role of TC-11

TC-11 addresses all three types of corrosion.

Oxidation – The TC-11 film prevents contact between the oxygen in the atmosphere and the metal it protects. The lack of an oxidation potential at the interface between the metal surface and the atmosphere means that no oxidation generated corrosion will take place.

Electrolysis – TC-11 is an excellent insulator. This means that even if an electrical potential exists between two metals, TC-11 will prevent the electrons from flowing between the two metals because the resistance of the TC-11 film is significantly greater than the electro-motive force.

The characteristics of TC-11 are not completely unique. What is unique about TC-11 is the duration of the TC-11 film in comparison to other products in its class coupled with the low cost of  TC-11. This is the driving force for the high positive cost benefit ratio associated with using TC-11. TC-11 is a “thinking man’s” product. TC-11 has many features that make it a completely new and unique product.

TC-11 does not have problems with wax formation. Wax is an effective way to control corrosion, but it is difficult to remove and it has few significant lubricating or penetrating qualities.

In many cases rust will form underneath the wax film if it is exposed to sunlight.

Multi-purpose-films that evaporate have a much lower cost benefit ratio than TC-11. They can accomplish the same objective, but the short duration of the films means results in significantly higher total material and labor costs over the lifetime of the equipment.

Paint and TC-11

The relationship between paint and TC-11 is similar to the relationship between paste wax and paint.

Automotive paint jobs are among the most sophisticated paint jobs available. The manufacturers go through extraordinary steps to achieve mirror like finishes, and the result can be an artistic and engineering masterpiece. The paint job will last indefinitely, as long as it is maintained.

Most of us are familiar with maintaining an automotive finish. It is a long and tedious process. First, you have to remove the dirt from the car with soap and water. Next, you have to apply a paste wax. Finally, you have to polish the wax. This can take from two to four hours for an average automobile, and it should be done at least twice a year.

Few if any owners or operators apply paste wax to equipment. The time required to do so would be substantial, and in some cases it is impossible. Paste wax works well on large flat surfaces with mild curvature, but it is ineffective on surfaces with sharp curves and angles.

TC-11 is an effective substitute for paste wax. TC-11 is not a replacement for past wax, but from a functional standpoint it does exactly the same thing. Paste wax and TC-11 replace the hydrogen and carbon molecules that are removed from the finish paint by sunlight. As long as either film is in place, the film will deteriorate and the paint will maintain its original condition.

 TC-11 does not have the appearance of paste wax, but most owners are not overly concerned about appearance when it comes to machinery.

A typical paint finish is presented below.

The underlying metal is typically free of corrosion.

The primer serves the purpose of placing a corrosion proof film on top of the underlying metal. In the case of steel, the primer is the oxide of the metal being protected. In the case of aluminum, the primer is zinc chromate.

The finish coat protects the primer coat from water, sunlight, chemicals such as sodium chloride, and oxygen.

The paste wax coat sits on top of the finish coat. When sunlight breaks the bonds between atoms in a  hydrocarbon molecule, it is a wax molecule that is destroyed. When water is sitting on top of the film of paste wax, there are no micro-pores to allow for the transfer of oxygen through the water to the underlying metal.  The same hold true for oxygen in the air: the paste wax film fills the micro-pores in the paint, and it is oxygen proof as well as waterproof.

A  typical TC-11 finish is presented here.

Paint_2

The underlying, primer, and finish coat are identical to the paste wax condition. From a functional standpoint, the film of TC-11 is identical to the film of past wax: it makes the paint waterproof and oxygen proof. TC-11 does not have the aesthetic appeal of paste wax, but this is not a major drawback in the case of equipment. TC-11 has the following benefits over paste wax:

  • Stops existing rust, paste wax doesn’t

  • Removes existing light surface rust, paste wax doesn’t

  • Prepares surface for painting, paste wax doesn’t.

We do not recommend using TC-11 for automotive, truck , mobile equipment, or van sheet metal finishes. In many non-sheet metal applications, TC-11 has significant benefits over paste wax.

Any situation that involves moving parts is impossible to paint. Unless the metal is highly corrosion resistant, as soon as the part moves the paint is scraped off and the corrosion starts. TC-11 is ideal in these situations, since in addition to preventing rust it is an excellent lubricant. TC-11 even frees frozen mechanisms, since it is a collection of corrosion bonds that prevent the components from moving. Most articulated mechanisms operate “in the dark”, so the TC-11 film lifetime may be measured in years, not months.

By using TC-11 to protect the equipment finish paint, you also lubricate the articulated mechanisms, free frozen fasteners, free frozen assemblies, remove light surface rust that is already in place, and prepare the surface for painting if need be. That’s why we call it “amazing”.

Oxidizing and Reducing Films

Oxidizing films are films that have a concentration of oxygen that is greater than the balanced  ratio between the fuel and the oxidizer. Most of us are more familiar with this term when it is referred to as the fuel/air mixture for the gasoline burned in your car engine.

In the case of metals, any oxygen at all creates an oxidizing film condition. Oxidizing films result in corrosion, since the oxygen combines with the metal to form oxide deposits.

A reducing film is the opposite of an oxidizing film. Too much hydrogen and carbon are available, which is a good thing. Reducing films do not result in corrosion, because the carbon and hydrogen do not generate an oxide reaction.

An example of a reducing film is presented in Figure 1.

Oxidiz1

Figure One

The layer of hydrocarbons is impermeable to oxygen. This means that even though the oxygen may be only a few thousandths of an inch away, no oxygen is able to penetrate the hydrocarbon film and react with the metal. This is true even if the film is underwater.

An example of an oxidizing film condition caused by paint failure is presented in Figure 2. A micro-pore in the paint film allowed oxygen molecules to come into contact with the underlying metal.

Oxidiz2

 

Figure Two

The oxidizing film condition is worse than it looks. The oxide film is highly permeable to oxygen. The oxygen reacts with the next available metal molecule, which is usually underneath a layer of  paint. The oxide reaction increases the volume of the metal molecule, so the paint is actually lifted off of the metal.

When this type of paint failure occurs over a large area, the equipment is often scrapped. If TC-11 had been used to maintain the paint, the lifetime of the equipment could have been increased significantly at a cost that is a small fraction of the replacement cost.