Most chrome plated parts are Shafts and Rams, generally straight round components. These can make ideal chrome plated parts, providing the chrome plating is specified correctly.
Why Cylindrical Parts Suit Chrome Plating
Cylindrical parts, i.e. long, uniform surfaces, are ideal for chrome plating. Here chrome can be deposited to an uniform thickness. In Hard Chrome Plating, chrome is deposited to a consistent thickness to allow dimensional recovery of worn parts or to achieve new specified dimensions for new parts.
Surface Preparation Before Plating
A ground and true round surface is required to be sent for plating. The bearing shoulders, thread ends and any ports or seal grooves need to be degreased and masked to prevent chrome depositing onto these areas.
Specifying Deposit Thickness Correctly
The deposit thickness for a shaft that is being restored to its original size should be calculated based on the worst worn diameter of the part. The amount of undersize that remains in the shaft after wear, plus the required finish grinding allowance (typically 0.05mm to 0.15mm per side) will give the required stock allowance in the chrome deposit. For new-build rams the chrome is typically plated to a fixed stock allowance and then ground back to the required tolerance after plating.
For Hard Chrome Plating, see https://www.poeton.co.uk/advanced-treatments/apticote-100-hard-chrome/.
Grinding and Finishing After Plating
Grinding to size after plating gives the correct running clearance, surface texture and final dimensions. The finish after plating can be rough and slightly oversized. A cylindrical grinding operation is used to bring the chrome plated shaft or ram to the required size and surface finish. For hydraulic rams the surface texture and roughness is measured and compared against the relevant measurement standards to determine the final Ra value.
When to Replace Rather Than Replate
Hard chrome plating will not fix a cracked core, signs of fatigue or when a shaft is significantly undersized (more than about 1-2mm under the normal diameter).
Getting the specification right the first time will prevent future problems such as components being returned under finished dimensions after subsequent grinding.