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.
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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.
Certain portions of the procedure involving determination of specimen weight [mass] have traditionally been performed in SI units, and corresponding inch-pound units are not included. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazards statements see 5. Current edition approved April 1, Published April Originally approved in DOI: Significance and Use 3.
A coating of zinc on iron or steel articles provides protection against corrosion. As the protection is provided by sacrificial loss of zinc, the degree of protection is proportional to the weight [mass] of zinc coating. Specifications for zinc-coated articles frequently provide for different classes of coating so that the purchaser can select the coating weight [mass] most suitable to his needs.
No further reproductions authorized. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available. NOTE 1It is advisable to use an inhibitor with acid solution for example, Hexamethylamine Tetramine or similar at the concentration level according to the manufacturers recommendations to prevent attack of the substrate.
Hydrochloric acid fumes are present, and hydrogen gas is evolved in the stripping process. Therefore, the test should be performed under conditions of adequate ventilation. A fume hood is recommended for large numbers of samples or where the test is to be carried out frequently over extended periods of time. Mixing must be done by slowly adding sulfuric acid to water due to the heat generated and possible splashing. Under no circumstances should the water be added to the acid. The mixing should be performed under an acid fume hood.
Sampling 6. Chemical Soc. Chemicals, BDH Ltd. NOTE 2For convenience in calculating test results in inch-pound units, the specimen should have an area of 5. The weight [mass] of coating in grams on a specimen of that area is numerically equal to the weight [mass] of coating in ounces per square foot of sheet. For results to be reported in metric units, the specimen should have an area of mm2 of sheet The specimen of wire may be of any length over 12 in.
Where a continuous length is not available, shorter lengths totaling over 12 in. Since the density of the steel is known 0.
Except as otherwise provided, the specimens should have a minimum area of 3 in. For very small items, several pieces may have to be stripped to obtain the minimum area. Procedure 7. After determining the weight [mass], immerse each specimen singly in the stripping solution and allow to remain until the violent evolution of hydrogen has ceased, and only a few bubbles are being evolved.
This requires about 15 to 30 s, except in the case of sherardized coatings, which require a somewhat longer time. The same solution may be used repeatedly until the time required for stripping becomes inconveniently long.
The temperature of the stripping solution shall at no time exceed F [38C]. After stripping, wash the specimens by scrubbing them under running water, dip in hot water, and wipe or blow dry. Determine the weight [mass] of the specimens again, to the same precision as in the initial determination.
If specimens were prepared to the dimensions as provided in Note 2, they shall be presumed to have an area of 5. When it is not possible to determine the area accurately, as in specimens from corrugated sheets, the thickness of the stripped sheet shall be determined to the nearest 0.
Acid-resistant paints or lacquers, acid-resistant tape, or mechanical devices fastened to the test specimen are examples of commonly used stop-off materials. Apply the stop-off to the specimen after the initial determination of weight [mass] and remove before the second determination of weight [mass].
Because of the possibility of moisture absorption during the stripping process, the stop-off must not be on the specimen during either weight [mass] determinations. Determine the coating weight [mass] on the second side subsequently without a stop-off on the first side. Alternatively, for specimens of uniform thickness of base metal, such as a piece of plate or pipe, determine the average thickness of the stripped specimen to the nearest 0.
ASTM A123 and G90 Specifications
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. Certain portions of the procedure involving determination of specimen weight [mass] have traditionally been performed in SI units, and corresponding inch-pound units are not included. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.