On July 17, 2012 EPA sent to Office of Management and Budget (OMB) their new proposed MACT (Maximum Achievable Control Technology) for hexavalent chromium. This is the final step prior to publication in the Federal Register, probably in August. The rule is aimed at plating shops and will do two things:
- Halve the permissable Cr6+ air emissions from chrome plating shops. Since plating shops account for 0.35% of all Cr6+ emissions in the US based on the EPA’s National Emissions Inventory, this will reduce Cr6+ in the air by all of 1.7 parts per thousand at most.
- At the same time ban the use of PFOS over the next 3 years. PFOS is a very stable, and therefore bioaccumulative chemical that is used in chrome plating baths to reduce Cr6+ air emissions.
What is the effect for most US businesses and consumers? Chrome plating is used on the tools that manufacture almost every product we use every day – plates for printing dollar bills, rollers to produce the steel and aluminum to make metal products from forks to fork lifts, molds for plastic products from toothbrushes to televisions, dies for stamping out everything from tiny cell phone connectors to coins and car doors. (Click here for more details on hard chrome alternatives.)
It is also widely used in aerospace and defense, both industries where safety is paramount. For that reason the Navy pointed out to EPA that they could not possibly qualify a safe alternative to PFOS in 3 years, and the same is true for the aircraft industry, where the landing gear and all the hundreds of hydraulic actuators that control every passenger aircraft are chrome plated. Why does it take so long to qualify an alternative as safe? Ask yourself next time you board a plane if you would much rather they just cut out most of that testing.
Trivalent chrome plating has been in use for years, but it is only useful for thin decorative chrome such as you see on Harley motorbikes (which is mostly Ni, by the way, but that is a different story). Despite the expenditure of many milions or dollars (and euros) nobody has yet been able to commercialize a way of using trivalent chrome for the much more difficult job of making thick, wear-resistant hard chrome coatings.
There is a qualified alternative, HVOF thermal spray coatings, which have been used on all new landing gear designs for a number of years. It cannot be used everywhere hard chrome is used, but it handles most of it, while aerospace-qualified electroless Ni can handle most of the rest, and Co-based electroplates are being introduced as well.
And for all of those production tools? There are some new electroplates based on cobalt and on nickel plating, and for some molds and dies there are ultra-hard PVD coatings such as TiN – a lot more expensive, a lot longer lasting, but not readily available for large tools.
But all those alternatives are more expensive, and there is always a tradeoff – the more it costs to make it here, the more it will be made elsewhere.
For more information see New Updates at the National Association for Surface Finishing at http://www.nasf.org/nasf-news.php.