Classification by Coating Weight
Galvanized sheets are classified primarily by the thickness of the zinc coating and the intended service environment. Common classes include ordinary galvanized sheets with coating weights from 40 to 275 g per square meter, reinforced galvanized sheets from 80 to 600 g per square meter, and heavy-duty galvanized sheets above 600 g per square meter. Coating weight is the key determinant of corrosion life.
Ordinary Galvanized Sheets
Ordinary galvanized sheets carry zinc coatings generally between 40 and 275 g per square meter and are used in normal industrial environments. They are mainly applied to general building structures, doors, windows, furniture, and light enclosures, where the primary function of the zinc layer is to prevent oxidation and corrosion of the steel base in mild atmospheres.
Reinforced Galvanized Sheets
Reinforced galvanized sheets have coating weights from 80 to 600 g per square meter, providing better corrosion resistance, wear resistance, and durability for special service environments. They suit high-temperature, high-pressure, and highly corrosive conditions such as industrial equipment, ducting, and structural members requiring extended maintenance-free life.
Heavy-Duty Galvanized Sheets
Heavy-duty galvanized sheets have coating weights above 600 g per square meter, with excellent anticorrosion performance for the most demanding service. They are used in marine engineering, chemical equipment, offshore platform construction, and other fields requiring extremely high corrosion protection, where coating life is measured in decades.
Classification by Processing
Galvanized sheets are also divided by base processing into cold-rolled galvanized sheets and hot-rolled galvanized sheets. Cold-rolled based sheets have smooth surfaces and a more attractive appearance after processing, suiting furniture, home appliances, and visible interior applications. Hot-rolled based sheets may show surface roughness but provide robust coating adhesion and are preferred for outdoor building structures, pipes, and heavy sections.
Lock-Forming and Formability Grades
For applications such as HVAC ducting and architectural cladding that use lock-forming or seaming, formability grades are specified to ensure the coating and base metal withstand bending without cracking or flaking. Coating adhesion is verified by bend tests, and the specified coating class must be matched to the forming severity of the application.
Frequently Asked Questions
How are galvanized sheets classified? By coating weight, service environment, base processing, and formability grade.
What coating weights are available? From 40 g per square meter for ordinary service to above 600 g per square meter for heavy duty.
What is a heavy-duty galvanized sheet? sheet with zinc coating above 600 g per square meter for marine and chemical service.
What is the difference between cold-rolled and hot-rolled based sheets? Cold-rolled based sheets have smoother surfaces; hot-rolled based sheets suit heavy outdoor structures.
Where are reinforced galvanized sheets used? In high-temperature, high-pressure, and highly corrosive environments.
How is coating adhesion verified? By bend tests that check the coating for cracking and flaking.