G60, G90, ASTM A123 -- what does it all mean?
Many of our customers call with questions regarding specifications.
One of the most common questions we get is regarding G60 or G90
coatings. While these designations do refer to a hot-dip galvanized
process, it is really referring to the continuous galvanizing industry.
These products are usually seen on items like corrugated roofing
and wall panels. ASTM A123 refers to the batch hot-dip
galvanizing process, like we perform daily here at Hubbell.
So beyond that simple explanation, what is the difference?
The 60 and 90 in the G60 and G90 are really referring to
coating weights. G90 products need to have .90 oz/sf of zinc to
meet the specification. This is a total weight for the piece, so it
really means .45 oz/sf on each side. This is equivalent to about
0.75 mils per side. Batch hot-dip galvanizing per ASTM A123
calls for a much higher zinc coating thickness. Standard structural
shapes 1/4" or greater in thickness require a minimum of 3.9 mils
(about 2.3 oz/sf) of thickness. If you compare the numbers, you
can definitely see the difference.
Want more information? The AGA has created a two-page comparison
of the products: