Bolts, Screws and Fasteners: What Finish?

We are all familiar with these small but vital components that literally hold together much of the vehicles, structures and devices that we use every day. Bolts, Screws and Fasteners have a wide variety of applications but often come into contact with dissimilar metals in harsh environments, leading to corrosion. As such various metal finishing processes are applied to extend part life and here is an overview:

Anodising- For parts that are made out of Aluminium. Anodising essentially increases the naturally occurring oxide layer on the surface thus producing a protective barrier with a good level of corrosion resistance. Anodising also allows for colour dipping so as parts can be readily identified.

Chemical Blacking- Also known as Black Oxide Coating, this is a process that can be carried out on both Ferrous and Stainless Steel parts. The advantage of this process is that it has minimal impact on the dimensional tolerances of the part and produces a matte black finish. Chemical Blacking will not provide wear resistance but when combined with oil/sealants can enhance components with a moderate level of corrosion resistance.

Zinc & Passivate- One of the most widely used metal finishing processes, nearly all metals can be electroplated with Zinc which provides a good level of corrosion resistance, especially considering its lower cost. Zinc plated components are passivated and sealed and there are a range of colour options allowing you to easily identify your parts.

Phosphate and Oil- Phosphate coatings are suitable for parts made out of Iron or Steel and will most often be combined with rust-inhibiting Oil. Phosphate coating prevents galling and is popular within the automotive industry.

Xylan Coating- Xylan is a family of coatings, typically containing PTFE and offering abrasion and wear resistance, they are especially popular for bolting systems in harsh environments such as offshore sea applications.

Silver Plating- Silver plating provides excellent corrosion resistance as well as anti-galling and anti-fretting properties, even at high temperatures. Obviously this is a more expensive process, but where you have fasteners that are subject to corrosion from a variety of chemical sources, and in high temperature environments then Silver Plating will greatly extend their part life.

Silchrome Plating offer one of the widest array of metal finishing processes in the UK which includes all of the above. We provide both manual jigging for larger parts and barrel plating in order effectively process larger batches of smaller parts such as bolts, fasteners and screws. We are ISO 9001 and 14001 accredited and based in Leeds, West Yorkshire.