One Galvanized sheet product coating weight index requirements
Continuous hot-dip galvanized/zn-fe-alloy coated steel plates and steel strips:
Hot-dip galvanized coating weight index is generally 40 ~225g/m2
Hot-dip galvanized ferroalloy coating weight index is generally 30 ~ 60g/m2
Continuous hot aluminum zinc alloy coated steel plate and steel strip:
The weight of hot aluminum zinc alloy coating is generally 30 ~ 90g/m2
Continuous electric galvanized/zinc shackle alloy steel plate and steel strip:
The index of electrogalvanizing layer weight is 10 ~ 90g/m2 commonly
Second for the galvanized layer weight detection
1. Punching sample
The specific sampling method and sampling method are shown in the figure.The standard stipulates that the area of a single sample shall not be less than 5000mm2.
Punch 6 pieces of sample, respectively representing the upper and lower surfaces.
2. Detection method
(1) the weight method
Process: sample weighing – dissolution – weighing again.
The difference between the weighing and the sample area is used to calculate the coating or coating weight per unit area.
The advantage is the absolute measurement, the disadvantage is the sample destruction.
The unit of measurement is g/m2 or mg/m2.
Executive standard:
National standard: GB/T1839
American standard: ASTM A 90/A 90m-07
International standard: IS017925 ISO 1460
(2) X-ray fluorescence spectrometry
A set of standard plates from low to high zinc plating was made to establish the relationship between the X-ray intensity of zinc and the coating weight.Then the ray intensity of zinc in the zinc coating of the sample was converted from the regression equation to the coating weight.The key point of the method is the preparation of standard samples.The unit of measurement is g/m2 or mg/m2
Standard: American standard: ASTM A 754/A 754M
Date: JIS G 3321
Summary:
The gravimetric method must be manually operated while the advantage of X-ray fluorescence spectrometry is that it is fast and can be automatically analyzed in batch.
There are also other instrument methods such as coulomb method, glow spectrometry, or direct thickness gauge to determine the thickness of the coating.The results of different methods will be different.But the products recommended in domestic and foreign standards are gravimetric or X-ray fluorescence spectrometry.In case of any discrepancy in the measurement results, the weight method shall be used as the arbitration method.
Because the coating weight of galvanized sheet is uneven in the direction of the width of the sheet, especially hot galvanized sheet, the coating weight of different positions is different.