Status of Chromate Metal Pretreatment Replacement Research at the University of Cincinnati

摘要

Among the replacements for chromate metal pre-treatments that have been proposed in recent years, those that are based on the use of organo-functional silanes are unique in terms of performance, broad applicability and ease of application In this paper a brief overview is given of some recent developments in our laboratory, i.e., obtained after the previous review of 2002. It was shown earlier that silane films obtained by simple rinses can be formulated by means of additives such as nanoparticles, colorants, and inhibitors. With these modifications the silane processes can now duplicate or outperform the performance of chromate conversion layers in terms of having a color for detection purposes, being applied from aqueous solutions with very low VOC, and exhibiting the capability to protect the metal substrate in a scratch (self-healing effect). It is now shown that addition of organic inhibitors to silane films can push the level of protection up to 1700 hours of salt spray resistance. Certain mechanical forms of corrosion, e.g., erosion corrosion can also be controlled. Preliminary results are shown of the development towards a self-priming coating ('superpri-mer') based on the use of mixtures of silanes and resins.