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Metal spraying touch-up of galvanised steel

2003

I would also like to learn the pre-treatment for touching-up the galvanised steel before application with an Cold Galvanizing Compound / Zinc Rich Paintaerosol? Does this application need blasting or something special else, or just touch-up by direct spraying?

Thanks,

Pinar Hasanoglu
- Turkey

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2003

Hi Pinar.

There's two ways to do a touch-up job.

The first method is the one you suggest yourself = just clean the damaged spot very carefully, and then add some zinc rich paint. The bad thing about this method is, that the quality of this paint touch-up is very difficult to measure. If a company is ISO 9002 certified or just serious, they repair damages by metallizing! And yes, you will have to blast the damaged spot before metallizing. The surface should be blasted to minimum roughness Sa 2Â. Use a Zn or Zn/Al metallizing thread.

Good luck,

Poul Søndergaard
- Denmark

There is also the possibility to retouch the area by brush zinc plating. Depending on size, no. of parts and desired quality it could prove to be the only process that meets your particular specification at a reasonable cost.

Guillermo Marrufo
Monterrey, NL, Mexico
2003

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2003

Mr. Marrufo,

I don't think that zinc brush plating will last in outdoor conditions compared to a metallizing job....sorry to disappoint you - but that's a fact!

If you repair a spot at a hot dip galvanized surface, which normally should last at least 20-25 years without problems, it'll look rather bad, when you'll see that the repaired spots (repaired by use of zinc brush plating) begins to rust after only 5-10 years in outdoor conditions :(

I agree that using zinc brush plating is a cheap alternative, but I also think, that it won't be good enough compared to metallizing!

Poul Søndergaard
- Denmark