Corrosion Class

Weight Loss/
Thickness Loss

External Environment

Internal Environment

C1, C2

＜10-200g/㎡
（1.3-25μm）

Country/dry area
low pollution

Heated/unheated buildings/neutral atmospheric environment

C3

200-400g/㎡
（25-50μm）

Urban and industrial atmospheric environment

moderate SO₂pollution
coastal areas with low salinity

Workshops with high humidity and mild air pollution

C4

400-650g/㎡
（50-80μm）

Industrial areas and coastal areas with moderate salinity

Chemical plant
swimming pool

C5-I(industry)

650-1500g/㎡
（80-200μm）

Industrial areas with high humidity and harsh atmospheric environment

Almost long-term condensate/heavily polluted buildings or areas

C5-M（ocean）

650-1500g/㎡
（80-200μm）

Coastal and offshore areas

Almost long-term condensate/heavily polluted buildings or areas

Category

DFT Range(μm)

（Contains Zinc-Rich Primer）
Least dft(μm)

Expected Anti-corrosion Years

C2

80

Low(2-5 years)

80-120

Middle(5-15 years)

160-200

80

High(＞15 years)

C3

120-160

Low(2-5 years)

160-200

80

Middle(5-15 years)

200-240

160

High(＞15 years)

C4

160-200

160

Low(2-5 years)

200-240

200

Middle(5-15 years)

240-320

240

High(＞15 years)

C5I
C5M

200-240

200

Low(2-5 years)

240-280

240(C5I), 280(C5M)

Middle(5-15 years)

280-400

280(C5I), 320(C5M)

High(＞15 years)