As one of the most common substrates for chrome plating, it is worth noting that steel can present a number of difficulties for successful chrome plating before and after processing the part.
Check Substrate Hardness First
The Hard Chrome Plating process adheres well to a wide variety of steel grades; however the hardness of the base steel must be taken into account. Steels of very low hardness can suffer deformation under load thus resulting in cracking of the plating. Where high surface stress is expected, it is advisable to work with a substrate of at least 40 HRC prior to plating. Where required, prior heat treatment of the steel is possible to raise the hardness of the substrate.
Plan for Hydrogen Embrittlement Relief
Steel can suffer from hydrogen embrittlement when electroplating. Relieving hydrogen in high strength steels above 1000 MPa tensile strength is critical to safe processing. For this reason relief baking at 190°C for a minimum of 4 hours after plating is standard practice which must be noted on the customers’ drawings.
Adhesion Varies Across Steel Grades
Stainless steel must be activated (etched) prior to plating in order to achieve adequate adhesion. Carbon and alloy steels generally offer little problem with adhesion. It is essential to assess the surface of the steel for scale, oxide and contamination. Any of these can cause problems with adhesion and must be removed by means of grit blasting or etching prior to plating.
Control Dimensional Build-Up Carefully
The plating rate for chrome is very uniform. This means that in general the chrome will build up evenly on all surfaces of an article. However, outside corners and edges will build up faster than flat surfaces and inside corners will thin out. This must be taken into account when setting up plate parts with internal bores or other recesses. Grinding such parts can be time consuming. If you are looking for Hard Chrome Plating, see https://www.poeton.co.uk/advanced-treatments/apticote-100-hard-chrome/.
Account for Edge and Recess Behaviour
External radius’ such as these form the boundary of chrome plated components. Chrome plating tends to build up faster on the radius of parts than in recesses or internal bores. Where a part has very deep profiles or internal bores it is advisable to fit auxiliary anodes in order to maintain an adequate plating thickness.
Ensure all the necessary information is included on the drawing or purchase order and the part can be reworked if required to meet your specifications.