10. Galvanic Corrosion

Galvanic corrosion occurs when two or more metals with different practical nobility are electrically connected and immersed in the same environment: the less noble metal experiences an increase in corrosion rate due to the presence of the more noble one. The effects of this coupling on the less noble and the more noble metal are discussed in this chapter and represented by Evans diagram. The main factors influencing the extent of corrosion rate increase are analysed: availability of a driving force for galvanic corrosion, its possible dissipation in cathodic overvoltage and ohmic drop in the electrolyte, ratio between cathodic and anodic areas. Finally, prevention of this localized corrosion phenomenon is briefly described.