Mistakes made when chrome plating can be very common, and are generally predictable. By being aware of these before specifying or commissioning a job for chrome plating, you can save a lot of time and money by avoiding rework.
Skipping Proper Surface Preparation
The chrome deposit will follow the surface of the part it is being chromed. So if the part surface has scratches, pitting, old plating, contamination, old oil, scale or rust then these will be reproduced on the surface of the newly chromed part. Therefore the substrate must be prepared by grinding or polishing to the required surface finish (Ra) and ensure all surfaces are completely clean and free of all oil, scale and rust before putting into the chrome bath.
Using a Substrate That Is Too Soft
For hard chrome to perform satisfactorily, the base material must be hard enough to withstand the coating being pulled off by the base material deflecting under load. Typical base material hardness is around 45 HRC for wear applications, and this must be confirmed with the plater before processing.
Leaving Gaps in the Masking
There is a high risk of unwanted deposits building up on edges and exposed surfaces where the masking does not cover all surfaces evenly. Areas such as threads, bores and datum surfaces that form part of the dimensional specification of the part require very accurate masking to maintain the tolerance and functionality of these areas. Ensure that you check the specification of the masking that your plater intends to use against your own specification before the job commences.
Ignoring Deposit Thickness in Your Dimensions
It is common for plated parts to be larger than their nominal dimensions after plating. In order to guarantee that parts fit together after plating, it is normal to dimension parts before plating to be slightly smaller than nominal to allow for wear after plating.
Chrome Plating is covered in more detail at https://www.poeton.co.uk/advanced-treatments/apticote-100-hard-chrome-plating.
Omitting Hydrogen Embrittlement Relief
Hydrogen Embrittlement is a common problem associated with electroplating high-strength steels (over 1000 MPa). Hydrogen that enters the substrate during electroplating can cause parts to crack some time after processing. Bake parts at 190 to 200 degrees C for a minimum of 4 hours after plating to allow the hydrogen to escape from the substrate.
It’s easier to get it right at the start of the process rather than stripping parts that have already been chrome plated incorrectly and incurring additional costs to replace them.