Chromated Free Galvanized Steel Deep Drawn Grade Zero Spangle Used For Home Appliances Board

What is Hot-Dip Galvanized Steel Coil?

Hot-dip galvanized steel coil is a type of steel that has been coated with a layer of zinc through a process called hot-dip galvanizing. This process involves immersing steel sheets or coils into a bath of molten zinc at temperatures typically ranging from 450°C to 500°C. The molten zinc reacts with the steel to form a corrosion-resistant, galvanized coating, which helps protect the steel from rust, corrosion, and environmental damage.

Hot-dip galvanized steel coils are widely used in various industries, including construction, automotive, home appliances, and infrastructure, due to their excellent corrosion resistance, strength, and longevity. The process of galvanizing adds a layer of zinc to the surface of the steel, which acts as a sacrificial barrier, corroding before the steel itself.

The zinc coating on hot-dip galvanized steel without zinc flower is uniform and durable, which enhances its ability to accept coatings, provides strong corrosion resistance, and results in a smoother and more aesthetic surface. In contrast, steel plates with zinc flowers are more susceptible to intergranular corrosion, leading to a reduction in corrosion resistance compared to the zinc flower-free steel. The presence of zinc flowers creates an uneven surface, making imperfections more visible after painting. Additionally, the use of lead and antimony in the zinc solution increases the heavy metal content of the zinc layer, which is not ideal for environmental sustainability.

• Environmental passivation is the traditional method, where the passivation film contains trivalent chromium. It is a widely used and effective solution for corrosion prevention.
• Chromium-free passivation eliminates chromium entirely, offering a more environmentally friendly option. This type of passivation provides better corrosion resistance compared to the environmental passivation film.
• Fingerprint-resistant passivation is specifically designed to address the issue of fingerprints causing rusting on the surfaces of household appliances during assembly. The passivation film in this case is completely free of chromium, aligning with high environmental protection standards.

The shape of the outer plates used in home appliances requires very precise standards, often surpassing the specifications for automotive panels. This is because home appliance outer panels are typically formed by simple bending and molding processes, and the majority of their surface remains flat. Any distortion in the plate shape can directly impact the appearance and the flat reflection of the appliance.

For instance, many refrigerator side panels are U-shaped, meaning the side panel is connected seamlessly to the top panel, often spanning over 3 meters in length. The thickness of these side panels typically ranges from 0.40 to 0.45 mm, making them both long and thin, with stringent requirements for flatness and shape stability.

Home appliance manufacturers, especially for refrigerators, specify that the unevenness (wave height) of steel plates used for side panels must not exceed 2 mm over every 2000 mm of length. This level of precision is critical to ensure the product's quality and appearance meet consumer expectations.