Engineering Partnerships That Outperform

Informative Articles

Design Recommendations For Hard Chrome Plating

Following is a list of recommendations when preparing machined surfaces for hard chrome plating. Contact us for more information or to request a quote.

How Machining Details Affect Plating

Condition of Machined SurfaceProblemRemedy
Sharp EdgesSharp edges produce a high current density condition that creates thick chromium nodules which are brittle and break or crack when ground.Do not terminate chromium abruptly on sharp edges. Instead, machine edges to have a 1/32 minimum radius before plating.
 the problem with sharp edges when hard chrome platingthe remedy for sharp edges when hard chrome plating
Inside CornersSquare inside corners produce a low-current density condition that creates a very thin chromium deposit to none at all near the inside corner.Never machine inside corners square. Instead, adopt the machining details shown below before plating.
  the problem with inside corners in hard chrome platingthe remedy for inside corners in hard chrome plating
Threads and SplinesThreads and splines combine the sharp edges and inside corners that were individually discussed. A thick chromium deposit builds up at the sharp edges of the thread crests and spline tooth tips, while a thin chromium deposit forms at the inside corners of the thread roots and spline tooth roots. This tapered deposit affects the thread and spline geometry.Mask threads and splines when chromium plating is not necessary. When chromium plating is required, radius the edges and minimize chromium thickness. Where heavy chromium deposits are required, machine the thread or spline with an allowance for the desired chromium thickness, then overplate and finish grind.
 the problem with threads and splines for hard chrome platingthe remedy for threads and splines for hard chrome plating

Chromium's Effect on Surface Finish

Chromium deposit thicknesses up to 0.002 inch have the same surface finish as the machined surface. Chromium deposit thicknesses over 0.002 inch show a progressive increase in surface finish with thickness. Chromium plating exaggerates the surface finish of shot-peened, liquid-honed, or dry-blasted surfaces.

Chromium never “levels” or “fills in” surface imperfections. Instead, defects such as pits, cracks, or scratches are amplified. For this reason, machines surfaces should be polished before plating; otherwise, their surfaces should be overplated and finish ground.

Specifying Chromium on a Blueprint

Prior to finalizing a specification, consultation with a U.S. Chrome engineering representative is recommended in order to take fullest advantage of the properties of chromium as well as to avoid potential problems.

Consultation covers such design parameters as:

  1. Selection of the desired type of chromium deposit: conventional, thin dense (crack-free), oil-retentive, etc.
  2. Location of the chromium deposit, and location tolerance.
  3. Best method of deposit control through masking.
  4. Deposit thickness and thickness tolerance.
  5. Machined part dimensions and tolerances before plating, to guarantee desired dimensions and tolerances after plating.
  6. Machined part surface finish and surface treatment before plating.
  7. Whether to chromium plate machined part to finish size, or overplate and finish grind.

Suggested Thickness and Tolerance

Service ConditionNominal Thickness of Chromium DepositThickness Tolerance of Chromium Deposit
Light corrosive atmosphere0.0002 to 0.0005 inch±50% of nominal thickness
Wear applications0.0007 to 0.0015 inch±50% of nominal thickness
Water and chemical attack0.002 to 0.005 inch±50% of nominal thickness

These thicknesses and tolerances are related to the size, shape, and surface finish of the machined part. Closer tolerances are often attainable but in production quantities.

We're ready to work with you.

We’re confident US Chrome will be your best option for your chrome plating applications because of our engineering approach, exceptional customer service, and regional locations. Contact us now with your questions or coating challenges.
We’ll help you find the right answer.