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Ref.: U.S. General Services Administration

URL: http://www.gsa.gov/portal/content/113034

Historic Preservation - Technical Procedures

Spectitle: Primers And Paints For Zinc And Galvanized Iron And Steel

Procedure code: 0501015S

Source: Us Custom House, New Orleans, La - Fromherz Engineers

Division: Metals

Section: Metal Materials

Last Modified: 02/24/2012

Details: Primers And Paints For Zinc And Galvanized Iron And Steel

PRIMERS AND PAINTS FOR ZINC AND GALVANIZED IRON AND STEEL

This standard includes general information on primers and paints tobe used on interior and exterior zinc and galvanized iron andsteel.

THE SELECTION OF A SUITABLE PRIMER AND PAINT FOR METALS

DEPENDS ONMANY FACTORS INCLUDING THE TYPE OF METAL TO BE COATED, THETYPE OFSURFACE PREPARATION TO BE USED, ENVIRONMENTAL AND SURFACECONDITIONS, DESIRED APPEARANCE AND PERFORMANCEREQUIREMENTS,METHOD OF APPLICATION, AND TYPE AND LEVEL OF EXPOSURE.CONSULT APAINT MANUFACTURER ALONG WITH THE REGIONAL HISTORICPRESERVATIONOFFICER BEFORE MAKING THE FINAL SELECTION.

Features which can be made from zinc or galvanized iron and steel

include gutters and downspouts, flashing, roofing tiles, crestingsand other decorative roofing features, and miscellaneous decorativefeatures made from pressed or folded metal sheets.

Galvanizing is the process of coating steel with zinc to protect itfrom corrosion. Three methods of galvanizing includes hot-dipgalvanizing, electrogalvanizing and cold galvanizing. Galvanizedsteel may be painted for many reasons, but the most importantreason is to provide additional corrosion resistance.

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The primary purpose of paint is to protect the metal from rust andcorrosion. To do so, paint manufacturers have developed paintsystems which are made to work together to protect the substrate.These systems include primers and appropriate, compatible top coatswhich can vary depending on the substrate and can vary betweenmanufacturers. As a result appropriate primers and compatible topcoats, both from the same manufacturer should be used.

For information on paint removal, surface preparation andapplication procedures, see the following:

- For guidance on paint removal from wrought iron, cast iron andsteel, see 05010-05-R, 05010-16-R, and 05010-17-R.

- For guidance on preparing metal surfaces for painting, see05010-05-R, 05010-16-R and 05010-17-R.

- For additional information on the history, properties and usesof paint, see 09900-01-S.

- See 09900-07-S for general guidelines on painting interior andexterior surfaces.

- For general information on galvanized iron and steel, see05010-09-S. Much of the same information will also beapplicable to pure zinc.

***PRIMERS FOR ZINC, GALVANIZED IRON AND STEEL***

TYPES

Oil/Alkyd Primers: Oil-based primers are to be used ONLY ON OLDAND/OR BADLY RUSTED SURFACES WHICH NO LONGER HAVEANY GALVANIZED COATING.

- Advantages: None. Not generally recommended for use ongalvanized metal.

- Limitations:

1. May react with the zinc coating on the steel to cause pooradhesion.

2. Generally not recommended for use on galvanized surfacesunless extremely rusted or weathered.

- Products/Suppliers:1. Benjamin Moore, #155 Ironclad Retard Rust Inhibitive Paint2. Red Devil, #9 Iron Oxide Primer3. Sherwin-Williams, E41 N1, Kromik Metal Primer4. Rust-Oleum, #7769, Rusty Metal Primer, or #5769, Red

Primer.

Zinc-rich Primers:

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- Advantages:1. Recommended for welded or damaged areas.2. Recommended for spot priming clean areas - areas where the

galvanized coating is missing or badly rusted.3. Good resistance to salt water.4. Normally used to protect steel from corrosion.5. May be used on iron.

- Limitations: None.

- Products/Suppliers:1. Rust-Oleum, #7785, Zinc Sele - use only latex top-coat.2. #770 Galvanized Metal Primer - use only latex top-coat.

Latex Primers:

- Advantages:1. Good adhesion.

2. Free of grease or oil.3. Good results on interior surfaces with no unusual

atmospheric conditions.

- Limitations:1. Not suitable for use in areas of high humidity or extreme

temperature changes.

- Products/Suppliers:1. Sherwin Williams, A-100, B42 N8, or Super paint series.

***PAINTS FOR ZINC, GALVANIZED IRON AND STEEL***

TYPES

The paint selected must be from the same manufacturer and madeto be used with the primer selected. It should also be selectedfor use in a specific situation where applicable.

- Intermediate and Top Coats: For the intermediate and top coat,use a paint from the same manufacturer as the prime coat, andone that is made to be used with that primer. Either oil-basedor latex paints may be used as recommended by the paintmanufacturer.

Apply using a brush to insure complete coverage.

- Allow the intermediate coat to dry according to manufacturersinstructions before applying the final top coat.

END OF SECTION