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Dissimilar Metals and Galvanic Coupling?

asked Mar 26, 2015 in Material by redonetti (1,280 points)
Can couplings between dissimilar metals be allowed?

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answered Mar 26, 2015 by guyredumis (540 points)
Galvanically induced hydrogen stress cracking can occur in metals under conditions that will not necessarily lead to cracking under un-coupled conditions. Therefore, couplings between dissimilar metals should be avoided as much as possible. When dissimilar metals must be connected, the cathode to anode area ratio should be minimized. For example, tubing in a heat exchanger should never be anodic to tubesheets or shells in order to prevent an unfavorably large cathode-to-small-anode area ratio.