We often see galvanized steel sheet, it is steel and zinc two kinds of composite material, combined with the advantages of both, both the strength and plasticity of steel, and corrosion resistant coating, in the field of construction, home appliances and automobiles have a wide range of applications.
In the atmosphere, zinc coating can give steel substrate excellent corrosion resistance, which is closely related to the thickness of zinc coating.How to identify the thickness of the zinc layer?Usually in the standard galvanized steel plate brand suffix.
For example, we often see the following suffix code
G90, Z27, Z275, 60, 90/90
These are labels for zinc thickness in different standards. To understand what they mean, you must know where they come from.
Then we have to understand what standard these coating suffixes belong to before we can make an analysis.
The above suffixes are classified into five standards, as shown in the table below:
| Standard Code | Unit | Zinc Coating Code | Zinc Coating Weight(both size) |
| ASTM 653/653M-13 | British systemOz/ft2 | G30 G40 G60 G90 G100… | 0.3 0.4 0.6 0.9 1.0… |
| Metric systemg/m2 | Z90 Z120 Z180 Z275 … | 90 120 180 275 … | |
| EN 10327-2004 | Metric systemg/m2 | Z100 Z140 Z200 Z225 Z275… | 100 140 200 225 275 |
| JIS G3302-2010 | Metric systemg/m2 | Z06 Z08 Z10 Z12 Z27… | 60 80 100 120 275… |
| GB/T 2518-2008 | Metric systemg/m2 | 60 80 100 120… | 60 80 100 120… |
| Q/BQB 420-2014 | Metric systemg/m2 | 40/40 50/50 70/70… | 80 100 140… |
In the table from top to bottom are: American standard, European standard, Japanese standard, national standard and baosteel enterprise standard.
Have you noticed a pattern: only in astm653/653m is there an inch marking method, and G90 is an inch marking method.
Characters in different standards have different meanings.
Is G90 equivalent to baosteel target 90/90?As can be seen from the table above, there are essential differences between them.
The value of comparison is only when the standards of measurement are consistent
The imperial value is certainly not the same as the metric value
The G90 USES the British unit, which must be converted to metric for comparison.
In the standard, G90 refers to the mean minimum weight of 0.9oz/ft2 (oz/ft2) measured at three points on both sides of galvanized sheet, namely 0.9oz/ft2.
1 oz = 0.0284 kg
0.9 oz = 0.02556 kg = 25.56 g
1 ft2 = 0.093 m2
25.56 g/m2 = 0.093 275 g/m2
G90= double side sum 0.9oz/ft2= double side sum 275g/m2 / baosteel enterprise standard 90/90 g/m?(90+90= the two-sided sum of 180g/m2).The relationship between zinc layer and thickness of zinc layer
The conversion relation between weight and thickness of each coating is different, which is described in the standard. The pure zinc coating 50g/m2 is approximately equal to 7.1um.
Then, for example, in G90, the total thickness of the zinc layer on both sides =275/50*7.1 =39.05um (micron).