Abstract:

Chromate conversion coatings and chromate based pigments are highly efficient in inhibiting corrosion of lightweight metals (e.g. aluminum and magnesium) but contain hexavalent chromium, a potential human carcinogen. On the other hand, in some cases, including steel, abrasion blasting of metals is used to prepare the surface, instead of a chromate pretreatment. However, the abrasion blasting process generates hazardous dust particulates, potentially causing environmental damage and negative health effects. This paper will discuss the development of a hybrid inorganic-organic pretreatment as potential replacement to chromate conversion coatings and abrasion blasting of metals. The pretreatment is based on a novel chemistry having a very high concentration of adhesive functional groups that form strong covalent bonds with the substrate and primer. Additionally, nanoscale corrosion inhibitor particles were incorporated into the pretreatment formulation to impart corrosion inhibiting characteristics. Adhesion and salt spray tests on test panels show that commercial primers applied over the hybrid pretreatment have similar performance compared to primers applied over abrasion blasted and chromate pretreated panels. Pretreatments containing nanoscale corrosion inhibitors showed superior performance in the salt spray test, compared to pretreatments without the inhibitors. DC polarization data is in agreement with the salt spray results, and also provides evidence of corrosion inhibition by the nanoscale particles, similar to that of chromates. The presentation will also discuss the addition of nanoscale inhibitors to commercial e-coat and powdercoat primers, and cyclic accelerated corrosion test (GM 9540P) on test panels coated with the commercial e-coat and powdercoat primres containing nanoscale inhibitors.

Acknowledgments:

The authors would like to thank the US NAVY SBIR program and the Department of Energy SBIR program for their support of the work presented here.