Surface treatments can be applied to give the product a nicer finish or to make it more manageable, although it is usually applied to protect against corrosion.
Corrosion is a chemical reaction that leads to the destruction of a material from the surface inwards. This process can render a material unsuitable for its purpose. Corrosion is most commonly caused by an (electro)chemical and/or mechanical disintegration. When choosing a surface treatment, it is important to take into account the environment in which fastening articles are going to be used. There are a number of fastening products made 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)