Backwards Thinking

My own hands on testing as well as outside research has given me a wealth of information that has helped my understanding of electrolysis immeasurably. While trying to describe how aluminum radiator and heaters give up enough electrons to leak coolant, I thought it might be fun to flip it around for a moment, and prove the inverse. Instead of trying to prevent aluminum from corroding, what if we were actively trying to remove electrons? What measures could we take to optimize aluminum corrosion? What lessons would we learn? Could we acquire any information that would be helpful in prolonging radiator and heater life spans?

Stay with me, because this will all make more sense in a minute...

When we think of aluminum corrosion and electron movement we focus on the part of the equation that affects us the most: the anodic part: the parts that leak and give us grief.  But for every electron lost at the anode, there is an electron gained at the cathode (in metalic bonding). If our (backwards) goal is to move electrons to the cathode, there are certain techniques and tips and tricks to help us accomplish this task. The commercial metal plating industry (like chrome plating and cadmium plating and zinc galvanized plating) knows a lot about how to optimize this process, and I was fascinated to learn a bit about this process and how easy electrons can move around with just a little encouragement.

I was also shocked when I realized that many of the same dynamics used in the metal plating industry to move electrons are found in an automotive cooling system, and I began to realize why electrolysis can get a grip on aluminum that sometimes seems impossible to break.

Since this discussion is about intentionally corroding out aluminum, lets get started OK?  In order to be successful in metal plating we need to make sure we have several factors accounted for:

Preparation for processing it for application of a non-metallic zinc phosphate for either corrosion protection or painting In metal cleaning it is generally overlooked that water plays the most important part. Its condition (hard or soft), and degrees thereof determines the performance of the chemicals dissolved in it. The efficiency of any cleaner is directly proportional to how if performs in water. The chemical must do three important things.

1. First, it must tie-up or inactivate hard water ions for better rinsing and cleaning.
2. Second, it must lower the surface tension of the water— in effect, it makes water wetter.
3. Third, it must ionize or dissociate when it is added to water.

An ion is an electrically charged chemical particle in solution. And in all acids and also in water the electrically charged particle is the Hydrogen ion. It is this ion that has such a pronounced effect on the activity or strength of an acid.

The counterpart of this ion in an alkaline water solution is the Hydroxyl ion, the degree of presence which determines the alkalinity of the solution.

Oxygen is the one chemical ion which is present in all alkalis, acids, water, and in air, and it is needed to maintain the chemical reaction known as oxidation. Two examples of this are: the rusting of iron or steel, and the white corrosion products on zinc plated surfaces. Also, Oxygen is the cause of breakdown or decomposition of certain chemical products. Although all acids and alkalis have an effect on all metals to varying degrees, some react so minutely that physical evidence is not observable. In the extreme cases. the reaction is violent, manifested in the form of boiling and gassing at the metal surface, which is a sign of a pronounced attack on the metal. In effect, the metal is being dissolved.

Generally, strong alkalis have the most drastic effect on aluminum and zinc, while strong acids more particularly attack steel. Strong oxidizing acids such as Nitric and Chromic readily attack copper alloys. Metal cleaning is decidedly affected by the type and degree of attack a particular chemical has on a given metal. Also of importance on the clean-ability of a chemical compound is the hardness of the water. That is, in the amount of calcium and magnesium dissolved, and the wetting ability. Other factors having a significant and influencing effect on the cleaning ability of a chemical compound are, namely

HEAT - The higher temperatures accelerate cleaning.

CONCENTRATION - of the chemical determines reaction time, speeding up removal of the soils and oils and greases from the surface by the simple reason that it brings fresh solution into contact with the contaminants, and the physical action itself helps to dislodge the materials clinging to the surface.

AGITATION - of the solution is desired for best results. Uniform cleaning and plating depends on consistently of the solution.

Remember, the above four factors are the most important ones to be learned, because all metal cleaning situations can be related back to one or all of them. If properly applied, these four factors will enable you to perform all your cleaning with a minimum of problems.
The tendency of oxygen-deprived locations to become anodic is the cause of many commonly-observed patterns of corrosion. 1

This illustration portrays Aluminum corroding, allowing a coolant leak.

Conclusion 

In order for us to optimize our aluminum corrosion (electrolysis) we we should make sure that we have addressed the following steps:

• Use pure water. By using de-mineralized, deionized or distilled water we can be sure that the water will do what we ask it. Hard water with dissolved calcium and magnesium will interfere with our efforts to move electrons away from the aluminum.
• Use Water Wetter. Make sure we use a surfactant. By using a surfactant we can ensure we have good contact with the surface of the aluminum.
• Start the engine. Make sure we have a heated electrolyte solution. Adding some heat energy to the process will shorten the time needed for electron movement, and amplify our results.
• Flush the cooling system. Make sure the aluminum is clean. The cleaner or newer the better. Be sure to use a flush that has Sodium Citrate as an ingredient, and make sure your in a hurry.
• Keep the engine running. Make sure there is sufficient agitation and contact. Make sure the water pump has plenty of time to move the electrolyte so it can be fully circulated from the anode to the cathode.
• Put some miles on it. If the solution is pressurized... so much the better. If our electrolyte is under pressure we can be sure that our aluminum has perfect contact with the electrolyte s well as allowing a higher temperature before boiling can occur.
• Run your de-gas bottle low. Making sure we have dissolved oxygen available will help continue our corrosion. Nothing beats the presence of oxygen when we are trying to corrode metal. Oxygen acts as a depolarizer, enhancing electron flow.
• Save and re-use the old coolant. To make sure we have an adequate electrolyte, be sure the coolant is several years old. Coolant that is either acidic or alkali makes a wonderful electrolyte.
• Add a ground wire. Encourage your aluminum to be an active metal by grounding it. Of course the ATF cooler contributes nicely as a rather nice grounding potential.

Obviously it is not our real intention to corrode an aluminum radiator or heater, but based on the recommendations above, we can optimize the electrolysis process in our cooling system by having a clean the metal surface, using a good electrolyte mixed with a surfactant, adding some heat, agitation, and oxygen. Before long we have moved enough electrons away from our aluminum to cause a leak in the wall surface.

This is an example of What-Not-To-Do in a cooling system with aluminum components, in fact the technical information comes from the metal plating industry. They know a few things about moving electrons from one surface to another...

Further In Depth Reading...

It's The Water | Too Much Information | Reserve Alkalinity | Step up to the Plate | Noble Metals | Anode Data | Energy | Hungry Water

1) Corrosion Drs, Stan Scislowski Basic Facts in Metal Cleaning