What is the difference between hot-dip galvanized and electroplated galvanized?

Hot-dip galvanized involves immersing the steel in molten zinc, producing a thick, alloyed coating of 3 to 5 mils. Electroplated galvanized deposits zinc by electrical current, producing a thin coating of 0.2 to 0.5 mils. For exterior applications, only hot-dip galvanized provides adequate corrosion protection.

Can I use galvanized nails with cedar siding?

Hot-dip galvanized nails can cause staining in cedar and redwood — the zinc reacts with the tannins in these woods and produces dark streaks at nail heads. For cedar siding and shingles, specify stainless steel nails.

Does galvanized steel need to be painted?

Not for structural or concealed applications where corrosion protection is the only requirement. For visible applications where appearance matters, galvanized steel can be painted after weathering for 6 to 12 months or after etching with a phosphoric acid wash. Prime with a galvanized-metal primer before applying finish coats.

Galvanized Steel — Old Canaan Building Materials

Galvanized steel is not a prestige material. It is a working material. It is the flashing under the copper that the copper covers. It is the nail in the cedar shingle. It is the strap hinge on the barn door. It is everywhere on traditional New England buildings in the places that are not meant to be seen, doing the work that the visible materials depend on.

The Character

Bright silver when new, weathering to a flat grey with a spangled crystalline surface pattern visible in raking light. The spangle is the zinc crystal structure — visible at the surface of hot-dip galvanized material. It is utilitarian and honest and it looks like what it is.

What It Is

Galvanized steel is steel coated with zinc by hot-dip immersion (hot-dip galvanized) or by electroplating (electrogalvanized). Hot-dip galvanized provides a substantially thicker, more durable zinc coating and is the correct specification for exterior building applications. Hardware — nails, screws, straps, hangers — for exterior work must be hot-dip galvanized or stainless steel. The distinction between hot-dip and electroplated is critical in a coastal or exposed environment.

How It Behaves

Hot-dip galvanized steel resists corrosion by sacrificial protection — the zinc corrodes in preference to the steel beneath. In a typical New England exterior application, hot-dip galvanized structural hardware lasts 50 to 70 years. In coastal salt-air environments, specify stainless steel for critical connections.

Why It's Right

Galvanized steel is correct for all structural fasteners, hardware, and metal components that are concealed or utilitarian in traditional New England construction. It is not a finish material. It is the working layer that makes everything else possible.

How To Get It

Hot-dip galvanized hardware is available from building supply dealers and specialty fastener suppliers. Specify "hot-dip galvanized" explicitly — not "galvanized," which may mean electrogalvanized. For structural connectors and joist hangers, specify G185 coating weight minimum for exterior exposure. For nails in cedar and redwood, specify stainless steel.

The Old Canaan Standard

Hot-dip galvanized steel, G185 coating weight minimum, for all structural fasteners, hardware, and concealed metal connections in exterior building applications in New England. Stainless steel for fasteners in cedar, redwood, and coastal applications. Not appropriate as a visible architectural metal finish. This is the working metal of the building envelope.

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