Will the stainless steel pipe be corroded
After corrosion, the passivation film on the surface of the stainless steel tube is destroyed and the passivation layer is dissolved. Such as common comprehensive corrosion: this type of corrosion is to destroy the surface of most of the material uniformity, corrosion surface is relatively uniform, usually occurs in inorganic
acid, non-oxidizing acid solution or hot strong corrosive solution, in the steel corrosion bottom area, this type of corrosion will be significantly enhanced. Such as residual welding oxide, carbon steel grinding down the powder layer.
Pitting (also known as pitting) : pitting is a small hole or rust spot formed locally on the metal surface with a certain degree of solubility. For example, chloride and olfaction can penetrate into the etched layer and cause passivation damage. Halogen halides in the etched layer hinder the center of gravity repair of the
passivation layer, so small gaps can cause rapid and concentrated pitting. Pitting starts with small cracks and gradually penetrates into the metal, where corrosion accelerates and forms a large, deep cavity near the surface. Pitting is difficult to detect at first and difficult to judge. The passivation layer on the surface of the
stainless steel tube has some dents or scratches and other defects, or stained with iron particles or dust, arc pits on the weld, pores, spatter, which may form a weak link in the passivation layer. When seawater is used as ballast, the system is not washed clean with fresh water, and pitting corrosion is very easy to occur.
Clearance corrosion: in the narrow clearance, such as flange or thread connection, the passivation layer in the gap may be destroyed, in the design, should be as far as possible to avoid the use of flange and thread connection, to avoid the combination of clearance. In the process of welding, should avoid biting the edge
and other phenomena.
Intergranular corrosion: intergranular corrosion occurs in chrome-poor areas, resulting in a decline in corrosion resistance, corrosion in a strong acidic environment. The carbon content of the stainless steel tube on the chemical ship is less than 0.03%, which increases after being heated for a long time. However, if the
steel surface is contaminated by oil, grease, coating and paint, it is prone to intercrystalline corrosion.
Stress corrosion crack: it is the austenitic stainless steel tube under the action of chloride ion, mechanical stress and temperature rise cracking, under 60° c and in the cargo tank rarely occur stress corrosion crack. It occasionally occurs in heating coils (heating semi-solid oil containing chloride ions or exposure to
seawater ballast tanks containing chloride ions).
Electrochemical corrosion: electrochemical corrosion of heterogeneous materials may occur because of the electrochemical liquid phase connection. When carbon steel and stainless steel tubes are welded, accelerated corrosion of the reactive metal carbon steel occurs. Driven by electrolytic voltage, the electrolytic
current between the two components causes electrochemical corrosion