Pre-painted Steel for Different Use Environments

According to ISO9223-2012, the corrosion of the atmosphere is classified into C1, C2, C3, C4, C5, and CX, which shows the corrosion degree from very low, low, medium, high, very high, to extremely high. So how to select suitable pre-painted steel for different use environments? Please keep reading for more details!

Typical Environments of Different Corrosion Degrees

Code	Corrosion Degree	Indoor Environment	Outdoor Environment
C1	Very Low	Dry and clean indoor environments, such as offices, schools, and museums.	Dry and cold regions, extremely low pollution, and low humid environments, such as deserts, the Arctic, and the Antarctic.
C2	Low	Low-pollution and low-frequency condensation indoor environments, such as warehouses and stadiums.	Temperate zone and environments with low pollutant concentration (SO₂≤5㎍/m³), such as villages and small towns; arid and cold regions and low humid environments, such as deserts and subarctic regions.
C3	Medium	Sites with medium-frequency condensation and moderate pollution, such as food processing plants, laundry rooms, breweries, and dairy plants.	Temperate zone, medium pollutant concentration (5㎍/m³≤SO₂≤30㎍/m³) or low-salinity atmospheric environment, such as cities, low-salinity coastal areas; subtropical and tropical areas, low-pollution environment.
C4	High	Sites with high-frequency condensation and heavy pollution, such as industrial processing plants and swimming pools.	Temperate regions, high pollutant concentration (30㎍/m³≤SO₂≤90㎍/m³) or high salinity environment, such as heavily polluted cities, industrial areas, moderate salinity coastal areas or areas exposed to deicing salt; Subtropical and tropical regions, moderately polluted environment.
C5	Very High	Environments with extremely high-frequency condensation and heavy pollution, such as mines, industrial caves, and not-ventilated workshops in subtropical and tropical areas.	Temperate and subtropical regions with extremely high pollutant concentrations (90㎍/m³≤SO₂≤250㎍/m³) or extremely high salinity, such as industrial areas, coastal areas, and coastal shelters.
CX	Extremely High	Sites with continuous condensation or exposed to high humidity and heavy pollution for a long time, such as not-ventilated workplaces where pollutants enter outdoors in humid tropics.	Subtropical and tropical, extremely high pollutant concentration (250㎍/m³≤SO₂) and extremely high salinity environments, such as extreme industrial areas, coastal areas, offshore areas, etc.

Solutions for Different Corrosion Degrees

As shown in the table above, C1 and C2 belong to low-pollution environments, such as rural and light-polluted urban areas. It is recommended to use the color-coated steel with Z120-180 galvanized sheet or AZ80-100 galvalume sheet as the substrate. And PE paint with a thickness of 5+ 15/7 microns is enough.

C3 is a moderately polluted environment, such as heavily polluted cities, general industrial areas, and low-salinity coastal areas. It is better to choose HDP-coated or SMP-coated or PVDF-coated prepainted steel with galvanized sheet (Z275 or more) or galvalume sheet (AZ150 or more) as substrates. The recommended paint thickness is 5+20/3+9 microns.

The C4 level refers to heavily polluted industrial areas or medium salt spray seaside areas, or high-salt and high-humidity indoor environments, such as winemaking workshops, swimming pools, and seafood processing workshops. We suggest choosing AZ180 GL sheets as substrates, and HDP, SMP, or PVDF paints. The front paint thickness is 5+20 microns, and the back paint thickness is 3+9 microns.

C5 environments are very corrosive, such as high humidity, high corrosion industrial areas, high salinity seaside areas, pickling workshops, electroplating workshops, paper workshops, leather workshops, dyeing workshops, etc. It is recommended to use AZ220 or above aluzinc sheets as substrate and PVDF paints.

In addition, for areas with high altitudes and strong ultraviolet rays, it is not recommended to use PE coating.