Surface treatments are sometimes applied to give the product a nicer finish or to make it more manageable, however it is usually intended for corrosion protection.
Corrosion is a disintegrative alteration of a material emanating from the surface, which renders the material unsuitable for its purpose.This is most commonly caused by an (electro)chemical and/or mechanical disintegration.The environment in which fastening articles are to be used should always be taken into account.There are a number of fastening products manufactured from non-ferrous metal or high-grade steel (stainless steel) that can be selected instead of a product with a surface treatment.
Various coatings are available, i.e.:
· Metallic (good protection, including hot dip / zinc plated and cadmium)
· Organic (extremely high protection, no hydrogen embrittlement, i.e. PTFE)
· Non-metallic (very low protection, i.e. phosphatising)
The metallic coatings can be applied in several different ways, i.e.:
· Galvanised (immersed in a bath and by precipitating the metal layer with alternating current, i.e. electrolytic zinc plating).
· From the melting phase (molten bath immersion and centrifugation, i.e. hot dip galvanising)
· By means of diffusion (tumbling with zinc dust, i.e. sherardising)
· Mechanical (tumbling until zinc has bonded, i.e. mechanical zinc plating)