First of all g90 is not a galvanizing specification.
Galvanized sheet metal g60 g90.
It is a coating thickness designation in the galvanizing specification astm a653.
Galvanized steel is the result of applying a protective zinc coating to steel to prevent it from rusting.
The corrosion resistance of the g type is directly related to the amount of zinc coating i e g90 will resist corrosion to the base metal longer than g30.
This specification is for hot dip galvanizing steel sheet using the continuous high speed galvanizing process.
Others available upon request.
If it is for outdoor use or in a high moisture environment i would always specify g90 just because it seems to make a difference over time.
Hot dip galvanized steel.
Deep drawing steel and extra deep drawing steel are designations described in the astm specifications for steel sheet zinc coated galvanized or zinc iron alloy coated galvannealed by.
G90 galvanized steel has a longer service life than g60 g40 and g30 galvanized steel because g90 galvanized steel has a heavier coating weight of zinc applied to it at 0 90 oz ft 2 as opposed to g60 galvanized steel at 060 ox ft 2 and so on.
The g90 would be more galvanized coating than say g60.
This makes it rust proof and easy to paint.
Galvannealed steel results from the dual process of galvanizing and annealing the steel.
I hope this helps.
Hot dip galvanizing is the process of coating iron or steel with a thin zinc layer by passing the steel through a molten bath of zinc at a temperature of around 860 f 460 c.
The g60 is the most common galvanized metal and determines the amount of galvanize on the metal.