Q:What is the principle of the anti-corrosion performance of Q235B galvanized steel?
A:The anti-corrosion principle is mainly based on a dual protection mechanism:
1. Physical barrier protection: The dense zinc layer on the surface isolates the steel from oxygen and moisture, preventing electrochemical corrosion reactions;
2. Cathodic protection: The electrode potential of zinc (-0.76V) is lower than that of iron (-0.44V). When the coating is damaged, zinc will be corroded first, thereby protecting the iron matrix (sacrificial anode effect).
This principle enables Q235B galvanized steel to have long-term rust resistance in humid, industrial atmosphere and other environments.
Q:What effect does the thickness of the galvanized layer have on the anti-corrosion effect?
A:The thickness of the zinc coating is positively correlated with the anti-corrosion effect: the thicker the zinc coating, the stronger its ability to physically isolate the corrosive medium, and the longer the sacrificial anode is consumed, which significantly improves the anti-corrosion life.
Q：What corrosive environments is Q235B galvanized steel suitable for?
A：Q235B galvanized steel is suitable for mild to moderate corrosive environments, such as: 1. Ordinary atmospheric environment (urban and rural areas, dry climate); 2. Industrial atmosphere (low concentration of acid and alkali, pollutants); 3. Humid non-marine areas (no strong salt spray).
It is not suitable for severe corrosive environments such as strong acid, strong alkali, high salt spray (such as coastal areas, chemical plants), and needs to be replaced with zinc-aluminum-magnesium coating or additional coating protection.
Q：Will welding destroy the anti-corrosion properties of the galvanized layer?
A：Yes, welding will partially destroy the corrosion resistance of Q235B galvanized steel for the following reasons: 1. Zinc layer burnout: High temperature arc (about 3000°C) will evaporate the zinc layer near the weld, making the exposed substrate susceptible to rust; 2. Porosity and cracks: Zinc vapor may mix into the molten pool, causing pores or microcracks in the weld, weakening the continuity of corrosion protection; 3. Remedial measures: After welding, the zinc slag must be cleaned in time, and the anti-corrosion layer must be repaired by spraying zinc-rich paint or cold galvanizing.
Q：What is the difference in anti-corrosion between Q235B galvanized steel and ordinary Q235B?
A：1. Anti-corrosion ability: Q235B galvanized steel relies on zinc layer isolation and sacrificial anode protection, and its anti-corrosion performance far exceeds that of ordinary Q235B without coating.
2. Service life: After galvanizing, the anti-corrosion life is greatly extended (more than 20 years), while ordinary Q235B needs to rely on painting and has a short maintenance cycle (3-5 years).
3. Applicable scenarios: The galvanized version can be directly used in humid/industrial environments, while the ordinary version is only suitable for dry indoors or occasions that require frequent maintenance.