Development of a chrome-free pretreatment
Researchers are currently developing a chrome-free pretreatment based on a chrome-free primer technology.
Currently there are no chromium-free replacements for traditional hexavalent chromium pretreatments commercially available for the corrosion protection of 2000 series aluminum alloys used in aerospace. Two approaches have been used to provide the military with chromium (VI) alternatives. One approach is the use of a chromium (III) based pretreatment, however, the process still contains chromium, and toxic forms of cobalt are sometimes used and present in waste streams. The other option is a system’s approach where the corrosion resistance of the conversion coatings are evaluated not as stand alone coatings, but rather as a complete paint coating system. One of several issues arising from this approach is that most of the commercially viable pretreatments are not conversion coatings, but rather adhesion promoters that do not provide inherent corrosion protection if the outer paint coatings are breached.
Further information:
Morris, E & Ray, C & Albers, R & McLaughlin, J & Bean, S & DeAntoni, J. (2019). Using Chrome-Free Primer Technology to Develop a Chrome-Free Pretreatment.