Hot-dip galvanizing: the plated parts after oil removal and rust removal are immersed in high-temperature molten liquid zinc for dip galvanizing, which is a physical process. Hot-dip galvanized square tubes are plated by placing pre-treated steel fasteners into a molten zinc solution to form a zinc and/or zinc-titanium alloy coating on their surface.
Author: Anna
Hot-dip galvanizing and cold galvanizing are two common metal anti-corrosion treatments, and there are significant differences between the two. Here are the specific differences between the two:
Generation principle and process:
Hot-dip galvanizing: the plated parts after oil removal and rust removal are immersed in high-temperature molten liquid zinc for dip galvanizing, which is a physical process. Hot-dip galvanized square tubes are plated by placing pre-treated steel fasteners into a molten zinc solution to form a zinc and/or zinc-titanium alloy coating on their surface.
Cold galvanizing: also called electro-galvanizing, is the use of electrolytic equipment will workpiece after degreasing, pickling into the composition of the zinc salt solution, and connected to the negative electrolytic equipment; at the same time, in the workpiece on the opposite side of the placement of the zinc plate connected to the electrolytic equipment in the positive electrode, connected to the power supply, the use of electric current from the positive electrode to the negative electrode of the directional movement of the zinc layer deposited on the workpiece. This is an electrochemical process.
Thickness of coating and corrosion resistance:
Hot-dip galvanizing: The zinc layer is thicker, usually reaching more than 10 μm and even up to 45 μm to 300 μm, and therefore has stronger corrosion resistance. Its surface is slightly rough, but the corrosion resistance is excellent.
Cold galvanizing: The zinc layer is thinner, generally between 3 μm and 15 μm, so the corrosion resistance is relatively poor. Its surface is smooth, but the zinc layer tends to peel off in humid environments.
Appearance and Usage:
Hot-dip galvanized: the outer surface is rougher and darker in color, usually appearing silver-white. Due to the production process, the surface may produce water streaks and drip tumors. It is usually used for steel fabrications for outdoor work, such as power pylons and large-size fasteners.
Cold Galvanized: The outer surface is relatively smooth and bright, with a yellowish-green plating for color passivation and a greenish-white plating for white passivation. It is generally used for rust prevention of indoor use parts, such as chassis bottom, panels, small-sized fasteners, etc.
Price & Yield:
Hot-dip galvanizing: The price is usually higher than cold galvanizing because of the relative simplicity of the process and its ability to be produced in large quantities, as well as the thicker zinc layer. However, its corrosion protection and practicality are greater.
Cold galvanizing: the process is relatively complex and cannot be mass produced, and the zinc layer is thinner, hence the price is relatively lower. However, cold galvanizing may be preferred in certain occasions where surface smoothness is required.
In summary, there are significant differences between hot and cold galvanizing in terms of generation principle, coating thickness, corrosion resistance, appearance and application, as well as price and production volume. The choice of which type of galvanizing to use should be based on the specific use environment and needs.