CHROMATIZING Aluminium chromate and its applications What we call as phosphating to steel an iron is called chromating for aluminium surfaces. Also it is knows as alodine coating. There are yellow, green and transparent chromating types. Yellow chromate coats Cr+6, green chromate coats Cr+3. Coating weight can vary according to application time and coating type. Drying temperature must not pass over 65 º C for yellow chromate and 85 º C for green and transparent chromate coatings. It is importat to provide clean, grease free surface before chromate application. If hot degreasing bath is prepared, caustic bath and following nitric acid bath can be used for pickling. On the other hand, acidic degreasing baths have pickling ability with itselves. Chromating and paint adhesion will be much better on pickled and degreased aluminium surface.

VCHROM - AL is a concentrated colourless liquid which can be used to produce colourless non-chromate films/coatings on aluminium and its alloys. This process is most suitable to provide under-paint corrosion and to provide good bonding of powder coats or liquid paints with the aluminium surface. VCHROM - AL poses no pollution problems as compared to chromate treatments. VCHROM - AL process is very simple and economical as mild degreasing and pre-treatment takes place simultaneously while giving a good colourless coating that suits perfectly well prior to coating or painting. If oil contamination is more on surface, separate cleaning in ALM-81 is recommended, using 3-5% concentration. USES : VCHROM - AL process can be used on any aluminium surfaces or on aluminium alloys. It may not be suitable on certain alloys or castings as it may tend to produce a superficial black film, which needs to be washed thoroughly well with water.