http://www.sescocp.com/tutorial.php and
SESCO, Inc. :: Cathodic Protection Engineering
Technically, four conditions must always be present to create a galvanic cell and for corrosion to occur. There must be two different metals, one acting as the anode, and the other acting as the cathode. There must be an electrolyte to provide a path for current to flow from the one metal to the other. And there must be a direct electrical contact between the two metals to complete the electrical circuit. The flow of current through the electrolyte is always from the anode to the cathode. Wherever electrical current leaves the anode to enter the electrolyte, small particles of iron are dissolved into solution, causing pitting at the anode. Wherever the current enters the cathode, molecular hydrogen gas is formed on the surface and the cathode is preserved and protected from corrosion.
If one of the four conditions of a galvanic cell is removed, corrosion cannot continue. It is the removal of one of the four conditions, to reduce or interrupt the flow of galvanic current, which is the basis for cathodic protection and all other forms of corrosion control.
For anyone working on any of the cells discussed in this thread, you should find the information on both links very interesting. I realize most of you probably already know all of this however, it never hurts to refresh and remember what it is you are trying to do. There are many gems in these links that make it worth your time to review. This information is based on the pipe industry, but is quite pertinent to what is being attempted on this thread.
Wishing everyone success.
Brad S
SESCO, Inc. :: Cathodic Protection Engineering
Technically, four conditions must always be present to create a galvanic cell and for corrosion to occur. There must be two different metals, one acting as the anode, and the other acting as the cathode. There must be an electrolyte to provide a path for current to flow from the one metal to the other. And there must be a direct electrical contact between the two metals to complete the electrical circuit. The flow of current through the electrolyte is always from the anode to the cathode. Wherever electrical current leaves the anode to enter the electrolyte, small particles of iron are dissolved into solution, causing pitting at the anode. Wherever the current enters the cathode, molecular hydrogen gas is formed on the surface and the cathode is preserved and protected from corrosion.
If one of the four conditions of a galvanic cell is removed, corrosion cannot continue. It is the removal of one of the four conditions, to reduce or interrupt the flow of galvanic current, which is the basis for cathodic protection and all other forms of corrosion control.
For anyone working on any of the cells discussed in this thread, you should find the information on both links very interesting. I realize most of you probably already know all of this however, it never hurts to refresh and remember what it is you are trying to do. There are many gems in these links that make it worth your time to review. This information is based on the pipe industry, but is quite pertinent to what is being attempted on this thread.
Wishing everyone success.
Brad S
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