The chrome plating thickness and chrome plating finish can affect how a part looks and how a part will perform. If the chrome plating thickness and chrome plating finish is not correct from the start then rework may be required to achieve the desired results.
Thin Deposits for Decorative Work
Thin deposits of decorative chrome are typically in the order of 0.1 to 0.5 microns in thickness. These are often applied over a nickel undercoat. Dimensional change is negligible and as such, no special tolerancing is required. The corrosion resistance is mild and the wear resistance poor. As such, these types of chrome plating are used for appearance only.
Thicker Deposits for Functional Parts
Hard functional chrome can be specified from a thickness of 25 microns upwards depending upon the wear and load conditions of the part. There is more on Chrome Plating at //www.poeton.co.uk/advanced-treatments/apticote-100-hard-chrome-plating.
How Build-Up Affects Dimensions
The chrome will build up on edge more than in the recess. If a shaft is to run in a tight clearance then the diameter prior to plating must be stated, not the pre-plated size. The finished size should then be stated on the drawing.
As-Plated Versus Ground Finishes
An as-plated surface will normally have a surface roughness figure that reflects the quality of the underlying substrate, so a well-prepared part would typically be around Ra 0.4 to 0.8 micron. However, many chrome plated parts require a ground or lapped finish, typically around Ra 0.1 micron to ensure good running or sealing of bearings.
Stating Finish on a Drawing
It is essential when ordering Chrome to clearly state on your drawing or purchase order the correct thickness and finish required. This will prevent confusion as to the required finish, and ensure that the component is produced on time.
Matching the chrome thickness to your requirements and the finish to your job is the best way to get it right the first time!
