rust prevention on ornamental iron
Eighteen inches off the ground is where most ornamental rust starts, along the bottom rail and the lower ends of the pickets. The figures kept at ornamental iron gates georgetown thetaxpayers point the same way, and humid spells in Georgetown, TX keep that zone damp long after the rest of the leaf has dried.
Where does rust start first?
Rust starts where water sits and air reaches the bare steel. The first places are the bottom rail, the tops of scroll cups, the weld seams and the cut ends of tubing. Open tube ends let water run inside, where no one sees the rust until a picket snaps. A bottom rail that sits on a wet slab rusts from the outside in, which is why leaves are hung a few inches clear of the concrete.
What does primer do?
Primer bonds to clean steel and gives paint something to hold. A zinc rich primer adds some sacrificial protection, so a pinhole in the paint does not run into a rust stain. Steel is wire brushed or blasted to bright metal first, since primer applied over mill scale or old rust fails within a year. Two coats of primer on edges and welds are better than one coat everywhere.
What does galvanizing add?
Hot dip galvanizing covers the whole frame, inside and out, in a layer of zinc. It protects tube interiors, weld seams and tight scroll joints that paint cannot reach. A galvanized frame with powder coat on top is the strongest system for Central Texas, and it lasts far longer than paint alone. Galvanizing is done before the final finish, and the weld areas are cleaned of spatter first.
How does sun change the finish?
Summer sun on a dark steel gate can push the surface far above air temperature, and the coating expands and contracts every day. Cheap paint chalks and cracks, while powder coat holds. South and west facing leaves age fastest, and a gate near Interstate 35 collects road grit that scratches the lower rails. A fresh coat of clear sealer or a repaint at the first sign of chalking keeps ahead of it.
What does humidity do?
Humid spells keep moisture on the steel for days, and morning dew soaks every joint. Sprinkler overspray adds minerals that stain and attack the finish. Aluminum and galvanized parts handle that wet far better than bare steel does. Pointing sprinklers away from the gate and wiping the bottom rail twice a year costs almost nothing.
How is a chip repaired?
A chip is sanded to bright metal, wiped clean, touched with zinc rich primer and then matched with a brush coat of the original color. This takes ten minutes and stops rust from creeping under the edge of the powder coat. A rust bubble left alone for a season grows into a patch that needs welding and a full refinish.