FAQ

FREQUENTLY ASKED QUESTIONS

Sometimes, the galvanized coating is shinier in some places than others. Why is that?

The galvanized coating appearance may either be bright and shiny resulting from the presence of an outer layer of pure zinc, or duller, matte gray as the result of the coating's intermetallic layers being exposed. Performance is not affected. Coating appearance depends on the amount of zinc in the coating.

Can I paint right over the galvanized coating? If so, what procedure should be followed?

Galvanized coatings can be easily and effectively painted, not only for aesthetics but also to extend the structure's service life. The age and extent of weathering of the galvanized coating dictate the extent of surface preparation required to produce a quality paint system over galvanized steel. ASTM D 6386, Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting, should be consulted for suggested surface preparation methods for galvanized coatings of varying ages.

How much weight will my material gain from galvanizing?

The weight of the article will increase by about 3.5 to 10% due to zinc picked up in the galvanizing process. Thicker steel pieces pick up lower percentages of zinc.

What is "white rust" and how can it be avoided?

"White rust" is the term mistakenly applied to wet storage stain, which actually is a milder corrosion product than white rust. Wet storage stain can be avoided by properly stacking freshly galvanized articles, avoiding unprotected exposure to wet or humid climates, or by using a surface passivation treatment after galvanizing. Wet storage stain typically weathers away once the part is in service. (True "white rust" is most commonly associated with galvanized cooling towers.)

How long can I expect my galvanized steel project to last in service?

Hot-dip galvanized steel resists corrosion in numerous environments extremely well. It is not uncommon for galvanized steel to last more than 70 years under certain conditions. To get a good idea of how long your project will last, see the service-life chart.

What is the suggested practice for marking steel to be sent to the galvanizer for processing?

Parts should be marked with a water-soluble pen or other pen suggested by the galvanizer. Permanent identification can be made using metal tags or weld beads, or by stamping.

Can I paint right over the galvanized coating? If so, what procedure should be followed?

Galvanized coatings can be easily and effectively painted, not only for aesthetics but also to extend the structure's service life. The age and extent of weathering of the galvanized coating dictate the extent of surface preparation required to produce a quality paint system over galvanized steel. ASTM D 6386, Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting, should be consulted for suggested surface preparation methods for galvanized coatings of varying ages.

Is there a way to provide for intentionally ungalvanized areas?

Yes, but because masking or stop-off materials may not be 100% effective, contact your galvanizer for suggestions.