A number in parentheses indicates the year of last reapproval. A superscript epsilon indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. Referenced Documents 1.
|Published (Last):||23 February 2016|
|PDF File Size:||7.67 Mb|
|ePub File Size:||12.48 Mb|
|Price:||Free* [*Free Regsitration Required]|
G90 First of all, G90 is not a galvanizing specification; it is a coating thickness designation in the galvanizing specification ASTM A This specification is for hot-dip galvanizing steel sheet using the continuous high-speed galvanizing process.
The designation G90 is simply a coating thickness of 0. The coating produced by continuous galvanizing is uniform, has sufficient ductility to withstand deep drawing or bending without damage to the coating, and consists almost entirely of pure zinc.
In the continuous process, the steel in sheet, strip or wire form is passed through the cleaning tanks and zinc kettles at a very rapid speed. The speed determines the coating thickness and can range upwards of feet per minute. This results in a thin coating of almost pure zinc with very little intermetallic growth.
Continuous Sheet Galvanizing A variety of coating weights are available, ranging from 0. The standard product is Class G90, which has 0. Batch galvanizing coating specifications are given in weight per surface area. The galvanized sheet coating parameters relate to the total for both sides of the sheet.
The sheet coating thicknesses must be divided by two for an approximate comparison. The two methods of hot-dip galvanizing, batch and continuous, produce very different products with different characteristics. The hot-dip galvanized coating consists of a series of layers of zinc-iron alloy with successively higher zinc contents towards the coating surface. The coating is unique in that it is metallurgically bonded to the steel substrate, with the coating integral to the steel.
The strength of the bond is measured in the range of several thousand psi. If you are simply trying to specify a galvanized coating thickness that is 0.
If you want a pre-galvanized sheet that can be formed into various shapes, then you will need to talk with a supplier of galvanized sheet. This lack of alloying also means pre-galvanized sheet is less abrasion resistant than steel galvanized using the batch process.
And both coatings protect steel from rust better than other corrosion protection systems. However, the coating thickness difference is significant. Each type of galvanized product, batch or continuous, has applications where it would be best utilized. The material provided herein has been developed to provide accurate and authoritative information about after-fabrication hot-dip galvanized steel.
This material provides general information only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability. The information provided herein is not intended as a representation or warranty on the part of the AGA. Anyone making use of this information assumes all liability arising from such use.
Was this answer helpful? Ask an Expert.
A number in parentheses indicates the year of last reapproval. A superscript epsilon indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. Referenced Documents 1. In the body of this test method, reference to zinc coating shall be interpreted to also include zinc alloy coating except where specifically stated otherwise.
ASTM A90 (2011).pdf
ASTM A123 and G90 Specifications