Zirconium-based pretreatments are being demonstrated by Army Research Laboratory, led by Fred Lafferman - project WP-201318, to test their effectiveness as a replacement for zinc-phosphate on steel and for chromate conversion coatings and etch-primers on aluminum substrates.
The use of zinc phosphate and chrome presents significant environmental and health concerns during their handling and application. Health hazards include heavy metal exposure, due to the presence of hexavalent chromium (CrVI or Cr6+), or Nickel (Ni). The use of wash primers presents an environmental hazard due to the release of hazardous air pollutants (HAPS) as well as possible chromate exposure.
The use of zirconium oxide pretreatment, pioneered by PPG with the development of ZIRCOBOND® and X-BOND™ treatments for automotive and industrial applications, offers a more environmentally friendly alternative to zinc phosphate and chromium-containing surface treatments. The zirconium pretreatments contain no hazardous air pollutants. The use of zirconium pretreatment technology also provides potential energy savings because it is processed under ambient conditions rather than at elevated temperature, as the zinc-phosphate requires. Less water is also necessary due to the fact that the zirconium uses fewer steps in the process.
Demonstrations of the application of zirconium treatment were conducted at Letterkenny Army Depot in Chambersburg, Pennsylvania and Marine Corps Logistics Base Albany in Albany, Georgia. The demonstrations consisted of treating parts and panels with the X-Bond zirconium pretreatment, followed by painting with military primers and Chemical Agent Resistant (CARC) topcoats. These were mounted onto vehicles at Marine Corps Camp Lejeune or placed along the seacoast at Cape Canaveral for increased environmental exposure.
The exposed parts and panels were inspected after one year in service. Results show the X-Bond zirconium pretreatment to perform equal to Cr6+ and better than Cr3+ on aluminum. On steel the zirconium treatment was equal to zinc phosphate on panels and steel lift hook hold-down D-rings, mounted on HMMWV’s. The zirconium treatment showed performance better than the zinc phosphate treatment when used in conjunction with zinc-rich primers on steel. An additional advantage to zirconium pretreatment is that it can be used on armor steel without risk of compromising the armor’s ballistic properties.
The performance of the parts and panels will be monitored for up to two years of exposure. Approval of the treatment to military specifications is expected to be completed in 2017 for steel and 2018 for aluminum.
Zircobond is a registered trademark and X-Bond is a trademark of PPG Industries.