Hydraulic cylinder rods in particular are exposed to hard sliding wear as well as contamination of the working fluid, therefore a correct plating specification must be established before the rod can be sent to the plating shop.
Clean and Prepare the Base Metal First
Pre-treatment of the rod prior to plating of any sort (including chrome) is necessary to address any corrosion, pitting or even tool marks on the surface of the rod prior to plating. Chrome plating replicates the surfaces of the base metal exactly and so if there are any pits in the surface of the rod of a depth greater than about 0.05mm then it is possible that pre-filling of the pits may be necessary prior to plating.
Choose the Right Coating Thickness
Plating thickness for wear rods is typically in the range 0.025 mm to 0.1 mm, depending on wear characteristics and rod diameter. Ensuring that finished dimensions are specified (including for example any required grinding) ensures that the rod can be ground to correct size after plating, and that stress in deposit is within acceptable limits.
Check the Surface Finish After Grinding
The as-plated surface will have a roughness of around 0.8 Ra and will require a cylindrical grinding and lapping operation to achieve a surface finish in the order of 0.2 to 0.4 Ra. This is necessary in order to achieve a smooth surface that will allow the wiper seal to function effectively and allow sufficient lubricant to remain on the rod surface under load.
Seal the Microporous Surface Where Needed
Chrome deposits are porous and contain fine microcracks in the plating. In corrosive environments these can allow the fluid to penetrate through the chrome into the steel beneath. It is recommended that where the rod is to be used in a salt contaminated or chemically aggressive environment, that a post-plate impregnation or thin supplementary treatment is discussed with the plater.
Inspect Against a Clear Written Specification
Once a chrome plated rod returns from the plating shop, check the coating for thickness, adhesion and surface finish. Use the written specification for these parameters. Relevant BS and ISO standards for electroplated coatings describe measurement of thickness, assessment of adhesion and general inspection criteria that can be used as the basis for acceptance or rejection.
There is more on Chrome Plating at https://www.poeton.co.uk/advanced-treatments/apticote-100-hard-chrome-plating.
Setting the right specifications before a part is sent for plating can save many dollars of rework time.