7. Corrosion

Corrosion can affect the service life of mechanical parts or assemblies in a number of ways:

• in the absence of dynamic stress, corrosion can lead to progressive cracking of statically loaded parts in an aggressive environment: this is stress corrosion;

• dynamic stresses are applied to the part, even though it has already been corroded; in this case, the failure is due to fatigue alone, initiated by corrosion pitting, which plays the same role as a notch;

• fatigue and corrosion act simultaneously; it is of course the latter case that leads to the greatest reduction in the fatigue strength of the metallic material. In general, with corrosion fatigue, the Wöhler curve no longer has an asymptote, and it is therefore no longer possible to determine a fatigue limit, as was the case...