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December 10 - December 14, 2018

What is the best primer system for galvanized steel?

Selected Answers

From Erik Andreassen of CPS on December 14, 2018:
There is no mention if the galvanised surface is aged or new. This should be taken into account before specifiying a suitable primer. In many cases, major manufacturers have removed etch primers from their assortment and rely on good epoxy coatings at a higher film build. Some contractors found it very difficult to keep their applications to under 25 microns If figures like this were exceeded, the coating could peel off. Surface preparation is also a major factor in the selection of primers. Often, specifiers would list the surface preparation for galvanised surfaces as sweep or brush-off blasting. This is extremely difficult for some operatives to achieve without damaging the galvanized surface. After washing, roughening of the surface with course sand paper is an alternative. tThis should be carried out to a degree where there is no damage to the substrate. If the substrate is relatively old, surface-tolerant primers can be a very good alternative to standard epoxy, followed by a final coat of polyurethane if appearance is required.

From Frank Gerace of O.W. Hubbell and Sons on December 13, 2018:
The American Galvanizers Associational has a guide, “Duplex Coatings- Painting Over Hot Dipped Galvanized Steel." Pages 9 and 10 of the Guide list appropriate paint and powder coat types. The guide can be found at:    However, a word of caution: alkyds should never be applied directly over unprimed galvanized surfaces. The zinc in the galvanizing produces alkaline salts that can react with the alkyd and lead to ‘saponification’ failure with blistering, peeling, and poor adhesion.

From Josh Skinner of The Sherwin-Williams Company on December 12, 2018:
Galvanized steel can be primed with epoxies, acrylics, wash primers, etc. Primer selection should depend on the desired outcome. Are you looking for a thicker "barrier" coating? Do you need abrasion resistance? Chemical resistance? Are you painting the steel for aesthetic purposes only?

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Tagged categories: Coating Materials; Galvanized steel; Primers; Substrates

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