ROTODIP

Rust, and the prevention of it, has long been high on the agenda of car companies, though sometimes not as high as it might have been! In the early days it was considered that a wipe down with solvents before being primed and painted was enough to protect the car’s body from rusting. Of course, many cars of the time had wooden-framed bodies with fabric covering, so rust wasn’t an issue (though rot may have been). After the Second World War few cars had fabric bodies, and by the 1950s many cars were built without a chassis, as in the Austin A30 and later Mini, or with unitary or integrated chassis, and most had steel panels. Rust, especially on Britain’s roads where salt was routinely used in winter to melt snow and ice, then became a major problem.

Once a panel is stamped from steel sheet, if the bare metal is not protected immediately it will begin to corrode. As panels had to be stored off-line or shipped to another plant, they required a protective coating. Unfortunately, if left alone for any length of time, these coatings could harden, making it difficult to remove them when painting was required.

There are three stages required before a car can be painted in its final colour. First, lubricating oils needed in the pressing process and protective oils needed to protect panels in storage or transit must be removed. Then a rust-inhibiting zinc phosphate followed by a chromic acid rinse provides pre-treatment of the metal, and finally a suitable rust-resistant primer is applied to every metal surface. The final colour top coat itself