Chromate Pretreatment Research Articles

The effect of sodium chromate pretreatment on mercuric chloride-induced nephrotoxicity

Sodium chromate (20 mg/kg, s.c.), which in male rats inflicted necrotic damage mainly in the P1 region (proximal part of the proximal convoluted tubules), protected against proximal tubular necrosis induced by 0.5 or 3.0 mg Hg2+/kg in the P2 (distal part of the proximal convoluted tubules) and P3 (pars recta part of the proximal tubules) regions. Histochemical staining for mercury indicated that chromate increased mercury deposition in those cells of the P1 region which were unaffected by chromate (had intact brush border) but did not decrease mercury deposition in the most severely affected P3 region. Chromate pretreatment actually increased mercury deposition in the kidneys of animals killed 24 h after the injection of 0.5 mg Hg2+. The protective effect was mutual. Cellular proliferation and fibrosis observed 4-5 days after chromate were prevented by injecting 0.5 mg Hg2+/kg 3 days after chromate treatment.

The Structures and Surface Composition of Chromate Conversion Coatings: An XPS and SEM Study

SummaryIn order to understand the mechanisms of adhesion of paints and lacquers to pretreated surfaces, topographical studies have been made of films formed on aluminium surfaces by ferricyanide accelerated Chromate pretreatment. Detailed XPS and bulk structural analyses were also made of a film with poor cohesive strength. Pretreatment resulted in a progressive smoothing of the original highly pitted surface remaining after initial alkali cleaning. The bulk of the film with poor cohesion was found to be comprised of layers of small (30–70 nm) particles with a surface chemical composition similar to that found for material in the surface of the film and typical of this type of pretreatment film. Similar but smaller particles are probably present on the surface although they have not been clearly resolved. Adhesion promotion is most likely to be due to the general smoothing of the surface or area increases due to the particulate nature of the surface. Cohesive failure of the films is more likely to be due to structural changes in the film than chemical compositional changes.

An XPS study of chromate pretreatment of aluminium

AbstractSurface analysis by X-ray photoelectron spectroscopy has been used, in conjunction with ion-beam etching, in order to study films deposited on aluminium surfaces before painting. Examples of both the chromate and the chromatephosphate series of pretreatments have been studied. The chromate film was found to consist mainly of hydrated chromium oxide, Cr2O3. XH2O (x=1 or 2), with a surface layer consisting of chromiumferricyanide or its decomposition products. The chromate-phosphate film consisted of mainly chromium phosphate, with smalle amounts of chromium oxide concentrated towards the metal/film interface. In both pretreatments fluorides were found at the interface between the film and the substrate. From the analysis, a general mechanism offilmgrowth is proposed.