Corrosion and Protection of Channel Steel

Corrosion and Protection of Channel Steel

Channel steel is a long strip steel with a groove shaped cross-section, belonging to carbon structural steel for construction and machinery. It is a complex section steel with a groove shaped cross-section. Channel steel is mainly used in building structures, vehicle manufacturing, and other industrial structures, and is often used in conjunction with I-beams. Due to its special metallographic structure and surface passivation film, channel steel is generally difficult to undergo chemical reactions with the medium and be corroded, but it cannot be corroded under any conditions. During the use of channel steel, various problems may be encountered, and corrosion is one of the more important issues. Corrosion of channel steel is generally caused by the following two reasons.

1. Chemical corrosion: Oil stains, dust, acids, alkalis, salts, etc. attached to the surface of channel steel are transformed into corrosive media under certain conditions, and react chemically with certain components in the channel steel, resulting in chemical corrosion and rusting; Various scratches can damage the passivation film, reduce the protective ability of the channel steel, and easily react with chemical media, resulting in chemical corrosion and rusting.

2. Electrochemical corrosion: Scratches caused by contact with carbon steel parts and the formation of a primary battery with corrosive media, resulting in electrochemical corrosion; The attachment of rust prone substances such as slag cutting and splashing to the corrosive medium forms the primary battery, resulting in electrochemical corrosion; The physical defects (undercuts, pores, cracks, lack of fusion, lack of penetration, etc.) and chemical defects (coarse grains, segregation, etc.) in the welding area form a primary battery with the corrosive medium, resulting in electrochemical corrosion.

Therefore, all effective measures should be taken during the processing of channel steel to avoid the occurrence of corrosion conditions and inducements as much as possible. One method is to use aluminum spray coating. Spraying aluminum coating and sealing with anti-corrosion coating can greatly prolong the service life of the coating. From the theoretical and practical application effects, zinc or aluminum sprayed coatings are the ideal bottom layer of anti-corrosion coatings; The aluminum spray coating has a strong bonding force with the steel substrate, a long coating life, and good long-term economic benefits; The aluminum spray coating process is flexible and suitable for long-term protection of important large and difficult to maintain steel structures, and can be applied on-site.

Another way is to use galvanized anti-corrosion protection: hot-dip galvanized channel steel can be divided into hot-dip galvanized channel steel and hot-blown galvanized channel steel according to different galvanizing processes. After rust removal, the steel parts are immersed in a molten zinc solution at around 440-460 ℃ to attach a zinc layer to the surface of the steel components, thereby achieving the purpose of anti-corrosion. In the general atmosphere, a thin and dense layer of zinc oxide is formed on the surface of the zinc layer, which is difficult to dissolve in water and therefore plays a certain protective role on channel steel.

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