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Classification of atmospheric corrosion environment

Writer： Hengfeng you electric Time：2023-05-09 views：times

The degree of corrosion damage of electrical distribution equipment varies greatly in different atmospheric environments. Therefore, when designing anti-corrosion engineering and formulating product environmental adaptability index, it is necessary to classify according to atmospheric corrosion environment. Because a large number of metal products are used in electrical distribution equipment, its operating environment is ever-changing, so it is inevitable to operate in corrosive environment. Today, we will let MARTIN of Hengfengyou Electric introduce to you the main anti-corrosion levels required for electrical distribution equipment in atmospheric environment.

Classification of atmospheric corrosion environment

There are generally two methods to classify atmospheric environment, one is according to climate characteristics, that is, classification of natural environment; The other is divided by environmental corrosion severity. The latter is closer to the practical application and is generally adopted. The international standard ISO9223-9226 is classified according to the corrosion rate obtained by the natural exposure test of the metal standard test sheet in the environment and the concentration of atmospheric pollutants in the comprehensive environment and the wetting time of the metal surface. The atmosphere is divided into five categories according to the corrosivity level:
C1：（Very low）
C2：（Low）
C3: （Medium）
C4：（High）
C5：（Very high）
Note: (The default anticorrosion grade of oil-immersed distribution transformer produced by Hengfengyou Electric is C3)
In the field of paint, the International Organization for Standardization has issued more targeted standards:ISO12944-1～8:1998 《Color paint and varnish -- protective paint system for corrosion protection of steel structure》（Paints and varnishes ─ Corrosion protection of steel structures by protective paint systems）This is a universally accepted and authoritative international standard for protective coatings and coating technology in the international anti-corrosion field. At present, this comprehensive standard is used in the process of spraying transmission and distribution equipment. Hengfengyou Electric focuses on the export of global transmission and distribution transformers, and the oil-immersed distribution transformers produced fully meet the anti-corrosion requirements and anti-corrosion grade of developed countries such as Europe and the United States≥C3。

ISO12944-1～8:1998 The standard specifies the atmospheric corrosion environment level and the corrosion environment classification of steel structures under water and in soil。Refer to ISO12944-5，You can design the coating system for a certain corrosive environment。Among them, the standard according to the corrosion of different atmospheric environment and the pollution degree of characteristic pollutants, the atmospheric environment facing the coating products is roughly divided into rural atmosphere, urban atmosphere, industrial atmosphere and Marine atmosphere four types.

FORM -1 ISO 12944-2Classification of atmospheric corrosive environment and examples of typical environment

Corrosion class	· Mass/thickness loss per unit area · （A year after exposure）				Typical environment in a temperate climate （FYI）
	Mild steel		Zinc		External	Internal
	Quality loss g/m²	Loss of thickness μm	Quality loss g/m²	Loss of thickness μm	External	Internal
C1 Very Low	≤10	≤1.3	≤0.7	≤0.1	-	Buildings with clean air, such as offices, shops, schools.
C2 Low	10～200	1.3～25	0.7 ～ 5	0.1～0.7	Low air pollution Mainly in rural areas	Dew can occur in buildings such as stadiums, air stations.

C3 Medium	200～ 400	25～ 50	5 ～ 15	0.7～ 2.1	In cities, there are industrial gases, moderate levels of SO2 pollution, or coastal areas with low salinity	Production plants with high humidity and some air pollution, such as food processing plants, laundries, wineries, dairy plants, etc.
C4 High	400～ 650	50～ 80	15～ 30	2.1～4.2	Industrial areas and coastal areas with moderate salt content	Chemical plant, swimming pool, sea ship, dock and so on.
C5-1 Very High（Industry）	650～1500	80～200	30 ～ 60	4.2～ 8.4	Industrial areas with high humidity and heavy air pollution	Temperatures are usually below the dew point in highly polluted areas
C5-M Very High （at sea）	650～1500	80～ 200	30～ 60	4.2～ 8.4	High salinity coastal or Marine	Ditto
Explain	1. The conversion values of corrosion levels used in this table are the same as ISO9223 2. In coastal, hot and humid areas, if the quality and thickness loss exceeds C5-M listed, then special attention should be paid to the selection of structural anticorrosive coatings

FORM-2 ISO 12944-2 Classification of water and soil environments for steel structures

Classify	Environment	Environment and architecture examples
1m1 1m2 1m3	Fresh water Seawater or salt water soil	River installation hydro power plant. Building structures in the harbor area, such as sluice gates, locks, etc., Marine structures. Oil storage tank, steel pile, steel pipe.

Note: When the atmosphere contains a variety of corrosive gases, the highest corrosion level should be taken as the benchmark.

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