Q: What’s the difference between galvanized and prime painted steel deck?
Bare Steel + Zinc
Bare Steel + Prime Deck Paint
Standard Coating Thickness
G60 (0.6 oz/sf) or G90 (0.9 oz/sf)
0.3 mil dry film thickness single coat
Roof Deck Applications
Recommended for corrosive or high moisture environments within the finished structure. (Highly corrosive or chemical atmospheres may require stainless steel, which is available from D-MAC).
For roof deck applications, it is recommended for dry, non-corrosive interior environments in the finished structure.
Form Deck Applications
Standard for floor form deck applications. The slab dead load may be deducted from the concrete design, as the permanent form will always carry this load.
May be used, but form must be designed as impermanent and therefore the slab dead load may not be deducted.
Composite Floor Deck Applications
Standard for composite floor deck applications.
Paint on the top side will interfere with shear bond and inhibit composite action. Therefore, it should NOT be specified. Acceptable finishes include: Bare steel top/painted bottom and galvanized top/galvanized and painted bottom.
Preparation For Field Painting
If bare galvanized steel decking must be field painted, ensure that any mill treatment is removed before priming. Instead, D-MAC recommends ordering galvanized steel decking that is prime-painted in the factory when field paint over galvanized steel decking is required.
Apply field paint over a small area and test for adhesion before painting the entire area.
Field painting is possible, but deck must be cleaned and prepped extensively before the field primer and finish coats are applied. To save field labor and potential adhesion issues, D-MAC recommends ordering galvanized steel decking that is prime-painted in the factory when field paint over galvanized deck is required.
Field Painting is recommended, especially where deck is exposed during service.
Dull grey top and bottom
Shiny silver top, dull grey bottom
Dull grey top, flat white bottom
Impermanent and provisional
Common Corrosion When Stored in Ordinary Atmospheric Conditions
Exposed edges and scratches are protected from corrosion by zinc, BUT “wet storage stain” or “white rust” will develop if water is trapped inside the deck bundles.
Exposed edges and scratches exhibit red rust. Water that flows into the bundle will create rust stains inside the bundles. Spray painting ends and edges upon receipt may reduce rust staining.
Jobsite Storage Recommendations
Deck bundles should be stored off of the ground with one end elevated to provide drainage and covered with a well-ventilated waterproofing covering.
See recommendation for Galvanized deck.
The most economical steel deck finish
>About 8% heavier than prime painted
About 7% lighter than galvanized