Steel gives lots of strength, but it has a weakness in that unprotected steel exposed to the weather oxidizes rapidly.  You see this in the form of red rust.  If the steel is unprotected, it will probably rust through it in a matter of just a few years.

To make the steel last longer, it is first protected by a coating of zinc or a mixture of zinc and aluminum.  The two coatings commonly used are galvanized and galvalume^®.  Galvanized is 100% zinc, while galvalume^® is 30% zinc and 70% aluminum.

Panels on Morton buildings are sometimes coated with galvanized and sometimes with galvalume^®, depending mostly on whether the panels are used for roofing or for siding.

The common coatings for galvanized are G90, which is 9/10 of an ounce of zinc per square foot, which is used by Morton.  Many others use a G60 galvanize coating, which is 6/10 of an ounce of zinc per square foot.  When galvalume^® is used on Morton buildings, we specify AZ55, which is a minimum coating of 55 hundredths of an ounce per square foot; whereas many others use an AZ coating, which is 5/10 of an ounce of zinc per square foot.

Here again, Morton uses the top of the line, whether our steel is protected by galvanized or galvalume^®.