Corrosion categories
ISO 9223 assigns atmospheric corrosion to corrosion categories C1 to C5, with each category stating a minimum and maximum corrosion rate for iron, zinc, aluminium or copper. In this way, reasonably accurate calculations can be made for particular corrosion categories in order to determine when a coating will reach the minimum value and initial maintenance will be required.
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Climate category
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Probability of corrosion
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Corrosion category outside
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Corrosion category inside
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|---|---|---|---|
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C1
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very low
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n/a
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Heated buildings with dry air and a clean indoor climate: hotels, offices, shops, schools.
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C2
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low
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Rural areas (inland), atmosphere with a low pollution level and low humidity.
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Unheated buildings where mild condensation is possible: storage facilities, sports halls.
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C3
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average
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Urban and industrial area with high humidity, moderate SO² pollution. Coastal zones with low salinity.
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Commercial premises with high humidity and low levels of air pollution: food industry, laundries, breweries, dairy farms.
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C4
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high
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Industrial and coastal areas with moderate salinity. High humidities and aggressive atmosphere. Chemical structures with constant humidity and contaminant levels.
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High humidity, moderate pollution: chemical companies, swimming pools, ports, ship docks.
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C5-I (Industry)
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very high
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Industrial area with high humidity and aggressive atmosphere.
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Areas and buildings with almost permanent condensation and a very high level of pollution.
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C5-M (Marine)
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very high
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Coastal areas and offshore areas with an aggressive atmosphere and high salt concentrations: offshore areas, offshore wind turbines, drilling rigs.
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Areas and buildings with almost permanent condensation and a very high level of pollution.
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Maintenance instructions
To preserve the lifespan, the correct and timely cleaning of the surface is necessary. The demonstrably thorough cleaning is a condition for the issued warranty. In the corrosion classes C2 and C3, demonstrable cleaning must be carried out at least once every six months. In the higher corrosion classes C4 and C5 and if there is non-irrigated surface in class C3, demonstrable cleaning must be carried out at least once per quarter. Pollution by chemical and organic means (including faeces) should be immediately removed in all cases.
The following (maintenance) instructions must be observed:
- Remove coarse dirt by spraying with tap water or RO water;
- Spraying with and allowing a neutral detergent to do its work and cleaning heavy soiling with non-abrasive tools;
- Cleaning agents must be chemically neutral with a pH between 5 and 8;
- Use of equipment that causes sanding scratches is not permitted;
- Rinse thoroughly with tap water or RO water;
- Highly contaminated objects can be cleaned with a polishing cleaner. Abrasives can only be used extremely sparingly if pollution has occurred locally, where ordinary cleaning methods are no longer sufficient;
- A post-treatment with a waxy product has the advantage that the gloss is obtained and the lacquer layer becomes more dirt and water-repellent.