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Best method for Color Coding music wire springs

April 13, 2010

I need to identify several similar springs with different colors. The springs are made from music wire and will be cycled anywhere from 5 million to 10 million times during their life. Springs are 3 in tall with an outer diameter of approx. .40 in

What types of plating and or finish is appropriate for springs that can give me several (2-4) color options and last the life of the spring?

I came across one spec that was "Zinc Plate Per ASTM B633 - Tint Red, Using Red Chromate".

Is this a sufficient spec for a plating shop?

Is Red Chromate toxic and inappropriate with respect to RoHS and or other safety or environmental standards?

What other colors are achievable with Zinc Plating?

What other finishing process are appropriate for this application?

Sorry for the number of questions in this post I am only trying to be complete to avoid being too vague.

Regards,

Brent H
mechanical designer - San Diego, California

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Zinc plating plus a chromate conversion coating is one option. The color of the chromate depends on the bath chemistry, and for clear chromates, a dye can be added to achieve colors like red. ASTM B633 only specifies the electroplated zinc coating, so you will need to specify that the chromate meets environmental requirements like RoHS, etc.

Another option is a pigmented organic coating applied in bulk by the dip-spin process. Doerken, Metal Coatings Inc, and Magni all offer these types of coatings in multiple colors. One last alternative is the Aqua-TRC line of coatings from JN Machinery. These have been developed specifically for this purpose, color coding of springs, rather than robust corrosion protection.

Toby Padfield
Automotive component manufacturer - Michigan, USA
April 15, 2010

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April 19, 2010

Toby,

Thanks for the information and your time this will help me narrow down the most appropriate method for our application.

Regards,

Brent Hutchings
mechanical designer - San Diego, California