Which corrosion protection method is the right one?
Depending on where they are situated, metals are subject to greatly differing corrosive influences and as a result, the demands on corrosion prevention also vary. These different influences are defined in corrosion categories C1 to CX.
C1 = Negligible:
- For example in heated buildings, offices, schools, stores, etc.
- Possible reduction in the thickness of unalloyed steel =≤ 1.3 µm (microns)
C2 = Low:
- Atmospheres with little pollution as well as unheated buildings with condensation, storage areas, sport halls, etc.
- Possible reduction in the thickness of unalloyed steel => 1.3 – 25 µm
C3 = Moderate:
- For example urban and industrial atmospheres with low SO2 pollution, low-salt coastal atmospheres as well as production areas with high humidity levels, laundries, breweries, etc.;
- Possible reduction in the thickness of unalloyed steel => 25 – 50 µm
C4 = Substantial:
- Industrial atmospheres and coastal atmospheres with moderate salt levels, chemical plants, swimming pools, coastal docks, etc.;
- Possible reduction in the thickness of unalloyed steel => 50 – 80 µm
C5 = Very high:
- Industrial areas with high levels of humidity and aggressive atmospheres, coastal atmospheres with high salt levels; buildings or areas with almost permanent condensation and heavy pollution;
- Possible reduction in the thickness of unalloyed steel => 80 – 200 µm
CX = Extreme:
- Offshore locations with high salt levels, industrial areas with extreme humidity and aggressive as well as sub-tropical or tropical atmospheres;
- Possible reduction in the thickness of unalloyed steel => 200 – 700 µm
A series of corrosion protection coatings are available for these corrosion categories which satisfy the demands presented by location, corrosion potential and the desired protection duration for the structure in question.
Normally coatings based on alkyd resin, acrylic resin, epoxy resin or polyurethane are used. All corrosion protection systems require a careful analysis of the initial condition and the careful preparation of the surfaces to be treated. Any existing corrosion, any loose previous coatings, dirt and contamination must be thoroughly removed. The basis of any coating system is the primer. Then one or more intermediate coats are added before the final layer is applied.