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Corrosion and design are synergistic. Design affects the type and amount of corrosion that is likely to occur, and corrosion affects the functionality of a given design. As galvanic corrosion can result in rapid localized attack, its effects are often severe.
The general relationship between open circuit potential, polarization, electrolyte resistivity, area ratio, and galvanic corrosion is well understood by corrosion engineers but is often not considered during design. Control of galvanic corrosion is most often accomplished by identifying probable sites for galvanic attack and either eliminating the possibility of galvanic corrosion through elimination of the dissimilar metals or by other means.
Where atmospheric exposure is encountered, mitigation of galvanic effects can be accomplished by eliminating design features that trap and hold moisture, the use of sealants, or the use of welded versus bolted joints. The selection of fastener materials must also consider galvanic compatibility.
In applications where the surfaces subject to galvanic attack are submerged, electrical isolation of dissimilar metals, control of the relative anodic and cathodic areas, the use of protective coatings, and the application of cathodic protection should be considered.
The technology to control galvanic corrosion is well known to corrosion engineers but is often not considered during the design process. It is the responsibility of corrosion engineers to insure that corrosion control technology is incorporated into the design process. This may be achieved either by education of design engineers regarding galvanic corrosion or by the inclusion of a corrosion engineer in the design team.
corrosion, galvanic corrosion, corrosion prevention, design, designers, design criteria, value engineering
Metallurgist, Naval Civil Engineering Laboratory, Port Hueneme, CA