Monday, October 20, 2008

Weld-Thru Primer Is Fragile

While working on the E9 yesterday I noticed something about the 3M Weld-Thru Primer I first saw while working on the rear window sill. This paint is extreamly fragile. I admit I did not use washeres with the bolts that held the patch in place for welding. Even so, the damage done by the wrenches is clearly visible in the second photo from yesterday's session. This confirms the advice I got from the experts at Redline Automotive, where I buy all of my paint supplies, which is that this coating must be removed before applying anything on the path to a permanent finish. Fortunately, the same characteristic that requires its removale makes is easy to remove.

As I was working in that area I was once again concerned about how to refinish the area behind the doubler with the large holes. It seems to me that if the existing finish is intact, all it needs is a good cleaning before applying POR-15. I am assuming that even though the finish is intact it is too old to reliably protect against moisture penetration.

Application with a conventional spray gun is out of the question due to the many hidden pockets and crannies. Brushing will be difficult for the same reasons. I am thinking about using a hand pump garden sprayer and a custom made sprayer, a tube with small slots cut into the sides. I recall something like this in a book on how to prevent corrosion. Perhaps if I had done what the book recommened I would not be in this situation.

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