The process flow and advantages and disadvantages of galvanized screws
Author: Marisa
I. Process flow of screw galvanizing
Screw galvanizing is to apply a layer of zinc on the surface of the screw to improve the anti-corrosion performance of the screw. The general galvanizing process includes the following steps:
1. Degreasing and rust removal: remove oil and rust on the surface of the screw to make the surface of the screw clean.
2. Cleaning: Clean the screws after degreasing and rust removal to remove impurities on the surface.
3. Pretreatment: Apply a layer of chemical composition on the surface of the screw to enhance the bonding force between the screw and the zinc layer.
4. Galvanizing: Immerse the pretreated screws in the galvanizing tank and plate a layer of zinc on the surface of the screw through an electrochemical reaction.
5. Drying: Put the galvanized screws into the drying room for drying.
II. Common ways of galvanizing screws
The ways of galvanizing screws are usually divided into three types: hot-dip galvanizing, electrogalvanizing and mechanical galvanizing.
1. Hot-dip galvanizing
Hot-dip galvanizing is to immerse the screws in a molten zinc tank at a temperature of about 450℃, so that the surface of the screws reacts chemically with zinc to form a layer of zinc-iron alloy. The surface brightness of the screws after galvanizing in this way is high and the corrosion resistance is good, but the cost is high and a large amount of zinc is required.
2. Electrogalvanizing
Electrogalvanizing is to immerse the screws in an electrolytic tank and plate a layer of zinc on the surface of the screws through an electrochemical reaction. This method can accurately control the thickness of the zinc layer and is suitable for micro-processing of screws. However, the zinc layer is thin and easily scratched.
3. Mechanical galvanizing
Mechanical galvanizing is to place the screws in a drum containing zinc debris for galvanizing. This method can be mass-produced and can handle screws of various specifications, but the zinc layer is uneven and easy to peel off.