Stainless steel that gets coated is no longer stainless steel. Stainless steel requires exposure to sufficient oxygen in order to maintain the protective oxide layer.
These are rudder bolts from the same gudgeon on my sailboat. The black stuff is anoxic corrosion.
Because the stainless steel is not stainless and a protective coating is optional, not standard like… you know, on every other car.
Stainless steel that gets coated is no longer stainless steel. Stainless steel requires exposure to sufficient oxygen in order to maintain the protective oxide layer.
These are rudder bolts from the same gudgeon on my sailboat. The black stuff is anoxic corrosion.