Paint Craters in Water Based Car Paint

A car manufacturer introducing a new prestige car found that small craters (circa 1mm diameter) were appearing in the pigment within the paint, necessitating a second paint application. Some colours were more affected than others. Despite extensive studies by the paint manufacturer and detailed chemical analysis of both the water used to dilute the paint and the finished paint in the crater areas, it was still unclear as to the real cause(s).

RPA were contacted to look at the water purification processes and to identify why the recently upgraded and extended water treatment plant had appeared adequate initially, but after a few weeks the problem had returned.

The principal reason for the cratering was found to be trace quantities of a range of water soluble organics. These caused the function of the dispersants for the pigment and other paint solids to break down locally. Pending the trialing and proving of additional water purification equipment, RPA evolved a simple treatment strategy utilising small amounts of the paint concentrate to react with the relevant organic contaminants, followed by centrifugal separation of the resultant flocks of pigment and paint solids. The remaining water, plus unaffected paint solids was then able to be used as the paint dilution water. The technique enabled the car to be launched on time in its full range of colours.

RPA also assisted the Client in ensuring that all the water treatment equipment was adapted correctly to overcome the problem permanently.

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