1, if the self-tapping screw surface accumulation contains other metal elements of dust or heterogeneous metal particles of the attachment, then in the moist air, the attachment and stainless steel between the condensate into a micro-battery, so that the protection film damage caused by self-tapping screws rust;
2, polluted air (such as containing a large number of sulfide, oxidized carbon, nitrogen oxide atmosphere), self-tapping screws in condensate, will form sulfuric acid, nitric acid, acetic acid liquid point, causing chemical corrosion;
3, self-tapping screws themselves of the composition of nickel and other trace of the element, time will be long and rusty.
4, self-tapping screws encountered acid, alkali, salt substances (such as decoration walls of alkali water, lime water splash), will cause local corrosion caused by local rust.