1.What are the advantages of Q235B galvanized sheet compared to ordinary steel sheet?
Extremely Corrosion-Resistant: The zinc layer isolates air and water from the substrate, allowing for long-term use in outdoor/humid environments (typically 10-15 years maintenance-free), significantly reducing the risk of rust.
Low Maintenance: No frequent painting or anti-corrosion coating is required, simplifying ongoing maintenance.
Machinability: Inherits the ductility and weldability of Q235B steel, allowing for bending, stamping, and cutting (only requiring proper zinc layer protection).
Elegant Appearance: The hot-dip galvanized layer produces uniform spangles, while the cold-dip galvanized layer is smooth, making it suitable for applications requiring minimal aesthetic appeal.
2.What are the disadvantages of Q235B galvanized sheet compared to ordinary steel sheet?
Higher Cost: The galvanizing process increases raw material costs, and the complex galvanizing process for thicker plates results in a more significant price premium.
Welding is Slightly More Difficult: The zinc layer easily produces zinc slag and fumes during welding (requiring specialized welding rods/wires, or pre-cleaning the welding area), which may affect weld quality.
The zinc layer is easily damaged: Bumps and scratches during transportation and installation can cause a "galvanic effect" in damaged areas, accelerating localized rust (repair requires re-application of zinc paste).
Limited High-Temperature Performance: The zinc layer has a low melting point (approximately 419°C). Prolonged exposure to temperatures above 300°C can lead to oxidation and detachment of the zinc layer, thus losing its corrosion protection.
3.What are the advantages of ordinary Q235B steel plate (ungalvanized)?
Lower Cost: Eliminating the galvanizing process, raw material prices are 10%-30% lower than galvanized steel (the specific difference fluctuates with zinc prices).
No surface coating interference: No zinc layer treatment is required during welding or painting (for example, cleaning zinc slag after welding galvanized steel), making it suitable for applications requiring complex subsequent surface treatments (such as spray coating and electrophoresis).
More flexible thickness selection: Ordinary steel sheet has a wider range of base thicknesses (from 0.3mm to tens of millimeters), meeting the needs of ultra-thick and ultra-thin structures (galvanized steel sheet is subject to process limitations, making galvanizing thick plates more difficult).
4.What are the disadvantages of ordinary Q235B steel plate (ungalvanized)?
Poor corrosion resistance: The base material is directly exposed to moisture, outdoors, or in dusty/moisture-rich environments and is prone to rust. Repainting is required within a short period (1-3 years) to prevent structural strength.
Long-term maintenance is cumbersome: Regular rust removal and repainting are required, especially in outdoor or high-humidity environments (such as chemical workshops and underground garages). Maintenance costs increase with age.
Short service life: Without effective anti-corrosion treatment, the service life of ordinary steel sheet is only 1/3-1/2 that of galvanized sheet. (For example, for outdoor steel structures, ordinary steel sheet will rust severely after about 5 years, while galvanized sheet can last for over 15 years.)
5.What are the corrosion resistance advantages of Q235B galvanized sheet and ordinary steel sheet?
Ordinary steel sheet: The base material is an iron-carbon alloy. When exposed to air, the iron undergoes electrochemical corrosion with oxygen and water, forming loose iron oxide (rust). This rust cannot prevent further corrosion from within and will continue to spread inward. For example, on unpainted outdoor ordinary steel sheet, noticeable rust will appear on the surface within 3-6 months, and the rust layer can reach a thickness of over 0.1mm in 1-2 years, compromising the structural load-bearing capacity.
Q235B galvanized sheet: It relies on the dual functions of "zinc sacrificial anodic protection" and "physical isolation":
- Physical isolation: The zinc layer tightly covers the base material, preventing water and oxygen from reaching the iron.
- Sacrificial anodic protection: If the zinc layer is damaged, the zinc's electrode potential is lower than that of the iron, causing it to corrode preferentially (protecting the iron base material from rusting), thus forming "cathodic protection."
As a result, galvanized sheet can remain intact for a long time even in outdoor rain or in humid salt spray environments at the seaside (which are not highly corrosive). It only corrodes slowly under extreme conditions (such as strong acids and high-concentration salt spray).