Galvanizing Technical Information

What standards does Emerald Galvanizing conform to?

photo: Emerald Galvanizing productsAmerican Society for Testing and Materials (ASTM), specific standards:

A 123  Zinc coatings on products fabricated from rolled, pressed, and forged steel shapes, plate, bars and strips.

A 153  Zinc coating on iron and steel hardware (fasteners).
The above ASTM specification(s) covers hot dip galvanizing coating thickness, finish appearance, and all factors relevant to acceptable galvanizing practices.

Upon request, Emerald Galvanizing can provide you with a letter of conformance to applicable ASTM specifications.

photo: Emerald Galvanizing productsASTM has a specification for the repair of hot dip galvanized coatings:

A 780 Repair of damaged hot dip galvanized coatings.
This specification describes methods that are used to repair hot dip galvanized coatings damaged by excessive rough handling during shipping or erection.  Additional information on this subject can be found at the web site for the American Galvanizers Association, www.galvanizeit.org.

What is “White Rust” and how can it be avoided?

“White Rust” is the term mistakenly applied to wet storage stain, which occurs when galvanized steel is tightly stacked or stored in boxes that don’t allow for free flowing air. Most wet storage stain can be easily removed with a cleaner or nylon brush. To prevent wet storage stain, store galvanized steel in an area where there is ample free flowing air between each galvanized article, avoiding unprotected exposure to wet or humid climates. Wet storage stain typically weathers away once the part is in service.

What is “cold” galvanizing?

There is no such thing as cold galvanizing. The term is often used in reference to painting with zinc-rich paint. Galvanizing (hot dip galvanizing) by definition means a metallurgical reaction between zinc and iron to create a bond between the zinc and the steel of approximately 3600 psi. There is no such reaction when zinc-rich paints are applied and the bond strength is only several hundred psi.

Can I paint over hot dip galvanizing?

Yes. Called duplex coatings, zinc and paint in combination (synergistic effect) produce a corrosion protection approximately 2-times the sum of the corrosion protection that each alone would provide. The key to painting or powder-coating over hot dip galvanizing is proper surface preparation accomplished through etching the material or by other abrasion means. Painting over galvanized steel that has been in service for many years also extends the life of the zinc coating. 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. A comprehensive guide to painting over galvanizing can be downloaded from the American Galvanizers Association web site, www.galvanizeit.org.

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