This is called pitting.
Basically, a mini galvanic cell is created which accelerates corrosion in a highly localised area. As the pit develops, the corrosion rate increases.
(Lovely positive feedback loop.)
Aluminium, chromium and stainless steels are the most susceptible, especially in an environment with chloride ions. Best prevention is a surface
treatment such as anodising, or to keep the metal clean, and preferably dry.
It can happen rather quickly. I am curious as to why you left your knife in salt water for so long. |