In consumer industries chrome is mostly known as the shiny, decorative plating used on automotive fenders and trim, steel office furniture, big Harley-Davidson motorcycles, and the grilles of those huge trucks that come right up behind us on the expressway.  However, these decorative applications use very little chrome (a few ten thousandths of an inch) and are not a particularly serious problem.  Far more serious is the use of hard chrome plating, which uses coatings several thousandths of an inch thick, often over large areas.  The chrome itself is not the problem.  The problem is that the hard chrome plating process produces large amounts of hydrogen gas, and the gas bubbles burst, throwing hexavalent chrome solution into the air as a fine mist.  In addition chrome plating produces large volumes of toxic waste.

Because of these emissions and wastes the EPA has mandated more stack emission scrubbing and lower emission levels. The EPA air emission limit for hexavalent chromium is 0.015mg/dscm.  OSHA has proposed new regulations in ID-215 (6-98) lowering the permissible exposure limit (pel) for chrome workers to 0.5mg/m3.

Figure 1.  Chrome plating pollution sources.ppt

Hard chrome plate is not easy to replace –

  • It is a very simple technology that is widely available
  • It is very versatile, used for wear resistance and for rebuilding worn components - a $1 to $2 billion business every year
  • It is relatively inexpensive (but becoming increasingly expensive as disposal, environmental, worker safety, and legal costs and risks continue to rise)

However, chrome plating was invented over half a century ago, and we have learned a lot since then.  Many modern coatings can now be used instead of chrome plating, and usually with better results (higher reliability, greater hardness, less wear).  Modern coating alternatives, such as thermal sprays are usually similar in cost to hard chrome (from 50% to 150%, typically), and are dropping in price while chrome is rising. 

There are a number of well-developed alternatives to hard chrome plating.  It seems that every week someone else comes out with yet another “hard chrome alternative”, most of which are not viable alternatives at all.  Determining which is right for your application requires evaluating the application and matching its requirements to the available technologies, then adopting (or adapting) them as needed.  The most widely used alternatives are

  • Electroless Ni and Ni composites
  • Thermal sprays – HVOF is becoming increasingly used in aerospace, while plasma spray use is growing in various industries, and finding increasing use for internal areas of items such as hydraulic cylinders.

Other alternatives are being adapted for replacing chrome.  Some of these may become broadly used, while others will remain niche products:

  • Ni-free electroplates and composites
  • Trivalent chrome is presently only in production for decorative use, but it is being developed for broader use in wear applications
  • Weld facing methods and microwelding such as electrospark alloying
  • Heat treatments and plasma nitriding
  • Laser modification, alloying, and coating methods


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Last revised: Wednesday, January 11, 2006