Metal finishing Q&As since 1989

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What is the difference between Corrosion and Electrolysis

I've been doing research on what types of pipes I should use. Many people talk about corrosion and electrolysis where galvanized steel touches copper. What exactly is the difference between corrosion and electrolysis? Travis

Travis Higley
student - Cummings , Ks, USA
2004

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"Electrolysis" is the electrochemical reaction that takes place at an electrode. There are two types of "active" electrodes, anode and cathode. Whe electricity is passed, the anode oxidises and the cathode reduces chemical species. The most common laboratory example of electrolysis is when electricity is passed through water: - you get hydrogen at the cathode and oxygen at the anode. However, another form of electrolysis is when two dissimilar metals are in contact and in an aggressive environment. This produces an electrical potential the size of which will be determined by their different positions in the electrochemical series. Once the electricity flows, the less nobel metal will oxidise and the whilst the more nobel metal provides a site for the other reducing electrochemical reaction to occur. This is known as "corrosion". Hence, "corrosion" can be considered as a the overall result of a specific type of electrolysis.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2004