How to Specify Zinc-Coated Steel Doors and Frames
Those of you with a few grey hairs may remember back in the day when bumpers used to fall off cars. Do you know why? Because manufacturers used to just put chrome plating on the steel instead of a zinc coating, which inhibits corrosion.
Fast forward to 2017 and zinc is the fourth-most consumed metal in the world, with half of that attributed to the galvanizing process. These days it’s just about everywhere including your steel door specifications. We still come across specs where the ideal zinc coating isn’t selected, so we’d like to explain the right way to do it.
Galvanized steel has that spangled look and is often found in coating weights of G40, G60, and we’ve seen specs with up to G90. The issue with these “G” coatings is that primer doesn’t stick very well to them so you’re hindering the second layer of protection with your steel doors. Although sometimes specified and manufactured, we do not recommend the G Type zinc coating for doors and frames.
Galvannealed steel is still zinc coated – without the spangled look – and is generally coated at A40 or A60. It is also known as “paintlok” for its excellent paint adhesion. Specifying galvanneal with a prime paint is the way to go with steel doors, and in fact, that’s exactly what you get if you specify to ANSI/SDI A250.8 (Specifications for Standard Steel Doors and Frames).
For a more information on galvanized and galvannealed coatings, please see SDI 112 (Zinc-Coated Steel Doors and Frames)
Modern Steel Openings
Building owners are increasingly requesting openings that are more secure but still look great. Architects have responded by specifying more steel doors with a vibrant pre-finish or wood grain finish. They are also opting for steel frames with smaller 1” profiles as opposed to the 2” that has historically been the norm.
Looking for modern design ideas for your steel doors? Use our Door Selector Tool to determine the appropriate performance and construction, then contact an SDI Certified manufacturer and take it from there.