Painting Galvanized Metal
I sometimes do projects that require painting galvanized metal such as maintenance on chimneys, which includes galvanized metal chimney caps. Painting galvanized metal is not difficult; but if the proper steps are not taken what seemed a great job can often suffer from premature peeling and flaking of the paint. Following the proper cleaning and prepping procedures and using the appropriate paint are critical elements for long term success when painting galvanized metal.
To prevent premature peeling of the paint, galvanized metal must be cleaned and prepped prior to painting. If the galvanized metal is new clean it with a water based house hold cleaner/degreaser to to remove any oil or other contaminates. Once dried, the surface should be wiped down using a cloth dampened with white vinegar, which is mildly acidic and will lightly etch the surface allowing for better paint adhesion. A final rinse with plenty of clear water will remove the acid. Painting the galvanized metal immediately after the rinse water has dried is recommended to prevent oxidation from forming.
The zinc coating on older galvanized metal may have started to oxidize, leaving a chalky residue on the surface. This residue is known as “white rust” and should be removed with a wire brush or light sanding, before cleaning the surface using the steps outlined in the previous paragraph.
Because of chemical reactions between some paints and the metal’s zinc coating, a good quality latex primer is recommended for painting galvanized metal. To achieve the longest lasting protection an additional two coats of quality latex paint should be applied over the primer.
Once the zinc coating has weathered past a certain point it no longer provides any protection and the surface of the metal will rust. Painting galvanized metal that has become very rusted requires a different procedure which can be found in the post, Painting Rusted Metal
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