On 10/03/2013 18:45, Gib Bogle wrote:
I want to check that I have the right procedure for dealing with
superficial rust on my galvanized steel roof. I understand that the
sequence is sand the rust off, wash with water, apply rust killer
(phosphoric acid), prime, paint. A couple of questions: Is it possible
to use the rust killer without sanding? The sanding step is the
hardest. Is primer necessary, or can I use another layer of the top coast?

You can buy anti-corrosion primers that need to be painted onto rusty
metal and then only need a top coat. Much quicker and easier. As it is
about 20 years since I used one on a corrugated iron roof that has not
needed treatment again, the name of the stuff has slipped my mind. I
bought it from an engineers' supplier, rather than a paint shop, but I
expect that professional paint suppliers will have something similar.

Colin Bignell