American Motorhome Paint Blisters

Several of our customers have asked me “Why do some of the body’s painted surfaces on motorhomes start to blister?”

There are two reasons for this happening one of which is a reaction. This reaction first of all starts to occur on some of the aluminium body strips and can also appear on the bottom of the lockers. The main reason for this happening is due to the type of primer paint that has been used.

Primer paint is used to produce a layer to which the paint can stick to, much the same as when you paint your interior doors at home. If you just paint on bare wood with top coat, paint it will go blotchy and won’t stick properly to the wood.

When you are priming aluminium you need to use an etch primer. This etch primer is acid based and basically eats into the aluminium microscopically enabling it to stick to the aluminium. If you don’t use an etch primer on the aluminium the paint will lift away from the aluminium and produce a surface that looks like blistering.

Here you can see the blistering.

Here you can see the blistering.

Now you would think it would be so easy just to prime the aluminium with etch primer. Well the answer to that starts with the price of the etch primer. Etch primer is more expensive than straight primer and also when using it, it takes longer to paint the aluminium. If etch primer is sprayed on first, it would have to be left to dry, and then rubbed down smooth, otherwise you would see a line in the finished paint work.

The second reason that can cause this problem is a process called electrolysis. This process happens when two dissimilar metals are used close together, for example steel and aluminium. It is visible and can often be seen when a steel pot rivet is used to join aluminium.

There is only one way to rectify this problem and that is to rub down the aluminium that is if the damage has not gone down too deep into the material. If it has, then replacement could be the only way to resolve the problem.

Electrolysis around the rivet.

Electrolysis around the rivet.

If you require any more information on bodywork give us a call on 01604 861999.