The importance of structural design has been discussed with reference to the prevention of galvanic contact and concentration cell effects, which may be the cause of serious weakening of the structure by localized corrosion (or pitting). Ledges or crevices where water and debris may be trapped in contact with the metal should be eliminated in the design as far as practicable. Welded seams can often be substituted for riveted seams. For instance, cracking of steam boilers due to the combined action of concentrated caustic solutions and high localized stresses in riveted seams has been practically eliminated by welding these seams.
Adequate drainage of metal structures exposed in the atmosphere renders the metal more or less self-washing or at least makes cleaning relatively easy.
Most of the failures from corrosion in service are due to local perforation or pitting. The average overall rate of attack uniformly distributed is rarely a matter...
