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Galvanneal surface rust

Had some galvanneal steel doors stored outside in the elements for about a year and they develop a reddish-brown discoloration (rust) on the surface. What do I need to do before painting? Do I have to have it re-galvlnized/annealed after removal of rust with wire brushing or could I just paint over it?

R.C

Roger Cooper
engineer - Hartsdale, New York, USA
June 8, 2011

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June 8, 2011

Galvanneal is a very thin zinc coating, not suitable for rust prevention in an outdoor situation. It did OK to last that long.
If you needed exterior protection, then hot dip galvanizing might have been suitable.
Now that you've got rusty doors, you need to get the rust off and put some protection on there.
Wire brushing rarely gets it all off, but shotblasting does.
When its clean get some zinc on there somehow. Could be a zinc rich paint, zinc rich powdercoating, or if the substrate is suitable then Hot Dip galv (in the latter's case the shot blasting will not be required as the HDG process deals with rust like this).

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

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August 1, 2011

Your job seems to a thin Galvanized sheets which is corroded / white rust.
There are many reputed brands of Zinc Ritch paints (Cold Galvanizing) are available in market.
To use it clean the surface and apply the paint. After drying you can use your own colour paint. It will work as good as Galvanized.

Umesh Dalela
- Mumbai, Maharashtra, India