Iron naturally exists as an ore in the form of oxides (Fe2O3), hydroxides (Fe (OH) 3), sulfides (FeS2), etc., and single iron is extracted and used by refining technology.
It is more stable to exist in oxides (Fe2O3) and hydroxides (Fe (OH) 3) than in iron, and when iron is left in the air, it naturally combines with oxygen and water in the air to oxidize. It changes into substances, hydroxides, etc. This phenomenon is called corrosion.
Corrosion is a phenomenon in which a metal is demetallized, but when a material comes into contact with a gas or liquid, a chemical reaction occurs and the material is altered or dissolved from the surface.
Corrosion does not proceed unless the conditions for corroding metals are met, but in addition to water vapor, oxygen, and nitrogen, various gases such as sulfur, sulfur disulfide, nitrogen oxides, and carbon dioxide are present in the atmosphere, causing corrosion. It will be a factor.
Metals contain impurities and, in the case of alloys, two or more kinds of metals, so there are non-uniform parts, but in non-uniform parts, the potential can be partially raised or lowered.
The high potential part (the noble ionization tendency) becomes the local cathode, and the low potential part (the low ionization tendency) becomes the local anode, causing a galvanic phenomenon, the anode part is melted and corroded, and the cathode part is corroded. It will be prevented.
The formation of a short-circuit battery in this way is called a local battery, and the corrosion caused by it is called local corrosion (battery action).
What is intergranular corrosion (intergranular corrosion)? Metal crystals are often polycrystalline, and the boundary between crystals generally has a lower potential than the crystal part. It becomes an anode and causes local corrosion.
Intergranular corrosion progresses toward the inside of the metal, which can reduce the life of the metal.
[Plating treatment effective for corrosion]
Electroless nickel plating
The electroless plating film is a nickel-phosphorus alloy containing a few percent phosphorus in a nickel-based film, which is harder than the nickel-plated film obtained by electroplating and has excellent corrosion resistance.
Hard chrome plating
A hard chrome plating (industrial chrome plating) film is a film with a beautiful bluish silver-white color tone, and has excellent corrosion resistance in the atmosphere.
Anti-rust coating "toughness"
Self-sacrificing anti-corrosion function, corrosion resistance in the course of rust and corrosion
Hot-dip galvanizing about 20 times more corrosion resistance
Connection Co., Ltd.
Please feel free to contact us for plating, coating, polishing, heat treatment, etc.
Consultations and quotations are free.
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