18 March 2019
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Retaining the edge

Whether the need is for added corrosion resistance or a change to the appearance of a part, TFC offers a range of finishing processes to ensure that retaining rings and springs perform the way that they need to in an application.

Some of the more common choices it offers include:

Oil dip: a standard finish for all TFC Smalley products produced in carbon steel. The oil provides resistance to corrosion in transport and in normal storage. However, the oil dip finish should not be considered a permanent finish.

Vapour degrease/ultrasonic clean: this is the standard cleaning process used for all stainless-steel parts. The process removes oil, grease, and other organic compounds from the parts’ surface. Ultrasonics are used as part of the process to force the solvent to act between the turns of the ring or spring.

Vibratory or hand deburring: these are optional processes provided to remove burrs and break sharp corners and edges that may occur on the gap ends, due to the cut-off operation after coiling. Circumferential surfaces and edges of Smalley parts are already smooth, on account of the nature of the flat wire, and do not require deburring.

Passivation: an optional cleaning process available for stainless steel, it provides a bright finish and increased corrosion resistance. Passivation dissolves iron particles and other substances that have become embedded in the surface of the material during production. If not dissolved and removed, these contaminants could promote rusting, discolouration or pitting in more corrosive environments.

Black oxide: a finish that provides a flat black appearance that is generally used as an aesthetic change, instead of an improvement in corrosion resistance.

Zinc plating. This is used on carbon steel to increase the corrosion resistance of the product. It is sometimes used as a more cost-effective alternative to other platings or stainless steel. Smalley’s standard zinc platings, Type V and Type VI, are RoHS compliant. Zinc plating does not guarantee coverage between the turns of multiple turn rings and springs. The process does subject the part to the possibility of hydrogen embrittlement. TFC offers stainless steel as a preferable alternative.

Zinc phosphate: also known as ‘Parkerizing’, zinc phosphate can only be applied to carbon steel. It appears grey-black in colour and has superior corrosion resistance to black oxide, but inferior to zinc plating or stainless steel.

Brian Wall

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TFC Europe Ltd


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