Zinc corrosion in galvanized steel is a common problem that is influenced by various factors. The following is a concise guide based on user shared experiences and insights:
Oxidation and corrosion: Galvanized steel is coated with a layer of zinc to protect it from corrosion. However, this zinc layer may be damaged, leading to oxidation and corrosion. If the zinc layer is damaged, normal oxidation reactions will occur beneath the zinc layer when water/moisture and air penetrate.
The effect of saltwater: Due to the increase in conductivity, saltwater also accelerates corrosion, as ions increase the conductivity of water and promote the transport of positively and negatively charged particles.
Thin zinc coating: Areas with thinner zinc coatings are more susceptible to corrosion. These areas with thinner zinc layers will show spots (for whatever reason), indicating that the base metal is penetrating.
Black spots: The edges of corroded spots may be darker than other parts of the surface.
Black metal: The metal in the middle of the spot may turn black, indicating the disappearance of the zinc layer and exposure of the steel. When zinc is depleted, iron and impurities react and turn black.
Correct coating: Ensure that galvanized steel has a uniform and sufficient galvanized layer.
Sacrificial anode: Using additional zinc or magnesium sacrificial anodes can help protect galvanized pipes. You'd better use magnesium anodes to protect galvanized and steel pipes
Surface treatment: Removing the galvanized layer before welding can prevent health issues and improve welding quality. Usually galvanized steel has a layer of zinc. You should polish the area you plan to weld, remove as much zinc layer as possible, and then perform anti-corrosion treatment on the interface after welding is completed.
Zinc smoke: Melting or welding galvanized steel releases harmful zinc smoke.
Protective equipment: When handling galvanized steel, use appropriate personal protective equipment (PPE) such as respirators.
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