Corrosion, however slight, is damage. Therefore, corrosion damage is classified under the four standard types, as is any other damage. These types are: (1) Negligible damage, (2) damage repairable by patching, (3) damage repairable by insertion, and (4) damage necessitating replacement of parts.
The term "negligible," as used here, does not imply that little or nothing should be done. The corroded surface should be cleaned, treated, and painted as appropriate. Negligible damage, generally, is corrosion which has scarred or eaten away the surface protective coats and begun to etch the metal.
Corrosion damage extending to classifications of "repairable by patching" and "repairable by insertion" should be repaired in accordance with the applicable structural repair manual.
When corrosion damage exceeds the damage limits to the extent that repair is not possible, the component or structure should be replaced.