U.S. General Services Administration
Technical Procedures Disclaimer
Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.
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We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.
This standard includes general information on primers and paints to be used on interior and exterior zinc and galvanized iron and steel.
NOTE: The selection of a suitable primer and paint for metals depends on many factors including the type of metal to be coated, the type of surface preparation to be used, environmental and surface conditions, the desired appearance and performance requirements, method of application, and type and level of exposure. Consult a paint manufacturer along with the regional historic preservation officer before making the final selection.
Features which can be made from zinc or galvanized iron and steel include gutters and downspouts, flashing, roofing tiles, crestings and other decorative roofing features, and miscellaneous decorative features made from pressed or folded metal sheets.
Galvanizing is the process of coating steel with zinc to protect it from corrosion. Three methods of galvanizing includes hot-dip galvanizing, electro-galvanizing and cold galvanizing. Galvanized steel may be painted for many reasons, but the most important reason is to provide additional corrosion resistance.
The primary purpose of paint is to protect the metal from rust and corrosion. To do so, paint manufacturers have developed paint systems which are made to work together to protect the substrate. These systems include primers and appropriate, compatible top coats which can vary depending on the substrate and can vary between manufacturers. As a result appropriate primers and compatible top coats, both from the same manufacturer should be used.
For information on paint removal, surface preparation and application procedures, see the following:
- For guidance on paint removal from wrought iron, cast iron and steel, see 05010-05-R, 05010-16-R, and 05010-17-R.
- For guidance on preparing metal surfaces for painting, see 05010-05-R, 05010-16-R and 05010-17-R.
- For additional information on the history, properties and uses of paint, see 09900-01-S.
- See 09900-07-S for general guidelines on painting interior and exterior surfaces.
- For general information on galvanized iron and steel, see 05010-09-S. Much of the same information will also be applicable to pure zinc.
Primers for Zinc, Galvanized Iron and Steel
Oil/Alkyd Primers:
Oil-based primers are to be used only on old and/or badly rusted surfaces which no longer have any galvanized coating.
Advantages:
- None.
- Not generally recommended for use on galvanized metal.
Limitations:
- May react with the zinc coating on the steel to cause poor adhesion.
- Generally not recommended for use on galvanized surfaces unless extremely rusted or weathered
Products/Suppliers:
- Benjamin Moore, #155 Ironclad Retard Rust Inhibitive Paint
- Red Devil, #9 Iron Oxide Primer
- Sherwin-Williams, E41 N1, Kromik Metal Primer
- Rust-Oleum, #7769, Rusty Metal Primer, or #5769, Red Primer.
Zinc-rich Primers:
Advantages:
- Recommended for welded or damaged areas.
- Recommended for spot priming clean areas - areas where the galvanized coating is missing or badly rusted.
- Good resistance to salt water.
- Normally used to protect steel from corrosion.
- May be used on iron.
Limitations:
- None.
Products/Suppliers:
- Rust-Oleum, #7785, Zinc Sele - use only latex top-coat.
- 2. #770 Galvanized Metal Primer - use only latex top-coat.
Latex Primers:
Advantages:
- Good adhesion.
- Free of grease or oil.
- Good results on interior surfaces with no unusual atmospheric conditions.
Limitations:
- Not suitable for use in areas of high humidity or extreme temperature changes.
Products/Suppliers:
- 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 made to be used with the primer selected. It should also be selected for use in a specific situation where applicable.
- Intermediate and Top Coats: For the intermediate and top coat, use paint from the same manufacturer as the prime coat, and one that is made to be used with that primer. Either oil-based or latex paints may be used as recommended by the paint manufacturer.
- Apply using a brush to insure complete coverage.
- Allow the intermediate coat to dry according to manufacturer’s instructions before applying the final top coat.