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Secondary processes and finishes for springs and wire components

24 October 2018

In the specification of springs and other wire components, secondary processes and finishes can be an important consideration.

They can help the design engineer to address environmental considerations or meet the needs of aesthetics in high value applications. These secondary processes can tailor the properties of the component to its application.

Plastic coating gives an aesthetically pleasing finish, with a coating up to 0.5mm thick. As well as looking good, the coating can be useful in applications where it is advantageous to have some cushioning between metal components. A good example might be a component inside a car, where you would like to avoid direct metal-on-metal contact.

It is important to note, however, that typical plastic coatings such as Nylon PA11 or PA12 are hydroscopic, so they suck in water. Further, the thickness of the plastic coating could interfere with the functioning of the spring.

An alternative to plastic coating is to paint the component, with electrophoretic painting and delta-tone finishing being two popular options. Electrophoretic painting is a very thin coating that can provide an aesthetically pleasing product finish. 

William Hughes employs a KTL-black electrophoretic process to deposit a shiny black, coating just a few microns thick on the spring – thin enough not to interfere with the functionality of the part. The coating can provide outside protection for up to 800 salt spray hours – enough to meet even some quite challenging environmental requirements.

High levels of corrosion resistance can also be provided by Delta-Tone finishing. This organic paint process is particularly suitable for wire components because of its flexible finish. It also has a low curing temperature, so there is no risk of changing the properties of the spring.

William Hughes can offer Delta-Tone finishing in a number of different colours, including red, green, blue, silver and black. Not only does this meet aesthetic requirements, it also enables components to be colour coded for easy identification in different applications. 

Another useful process is passivation. Primarily a cleaning process, it is typically applied to stainless steel components to remove any particles that might remain on the component after machining or grinding, thus preserving the corrosion resistance of the part. Such is the quality of William Hughes’ passivation process that the company has been awarded Nadcap accreditation for the supply of parts to the aerospace industry.

With the availability of a full range of secondary finishing and painting processes, William Hughes is well placed to advise on the most suitable finish for a specific spring application. 

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