In the manufacturing process of bolts and screws, surface treatment is an essential and very important process. It can not only improve the surface brightness of bolts, but also enhance their performance and prolong their service life.

Electroplating is the most commonly used surface treatment method for screw and bolt fasteners. It not only has a lower cost, but also the appearance of the electroplated screw fasteners is more beautiful, which can enhance the corrosion resistance of the bolts and extend their service life. Common iron materials such as hexagonal bolts, Allen bolts, self tapping screws, and drill tail screws use electroplating technology to enhance the anti-corrosion performance of the bolts.There are also many choices for the materials used in electroplating.

  

Galvanizing is the most commonly used surface treatment method for electroplating screw fasteners, including colored zinc (yellow zinc) plating and blue white zinc plating.Generally, screws that have been electroplated with zinc can pass the neutral salt spray test without producing rust spots within 24 hours, and those with high requirements can reach more than 72 hours.

Chromium plating has good corrosion resistance, but the cost of waste liquid treatment during the cadmium plating process is high and expensive.The chromium coating on screw fasteners is very stable in the atmosphere, not easily discolored or lose luster, and has high hardness and good wear resistance.

The use of chrome plating on fasteners is generally for decorative purposes, especially in bathroom fasteners. It is rarely used in industrial fields with high anti-corrosion performance because good chrome plated fasteners are as expensive as stainless steel materials. Only when the strength of stainless steel is insufficient, chrome plated fasteners are used instead.

Nickel plating on bolts is mainly used in places where both corrosion resistance and good conductivity are required. It is mainly used in fasteners for new energy vehicle wiring harnesses and is relatively rare in ordinary industrial and daily life.

Blackened surface treatment has little rust prevention ability, so it will rust quickly without oil coating. Even in the presence of oil, its salt spray test can only reach 3-5 hours.But this method is the cheapest, usually iron hexagon bolts and hexagon bolts are more commonly used

Phosphating the surface of screw fasteners is cheaper than electroplating, but its corrosion resistance is inferior to electroplating.The commonly used phosphating methods for screw fasteners include zinc based phosphating and manganese sand phosphating. Zinc based phosphating has better lubricity than manganese based phosphating, and manganese based phosphating has better corrosion resistance and wear resistance than galvanized ones. Its resistance to high temperatures can reach 225 to 400 degrees Fahrenheit (107-204 ℃).The dry wall nails we often use are usually treated with phosphating.

Bolt passivation treatment is the process of dissolving iron pollutants hidden on the screw during passivation, forming a passivation protective film on the surface of the screw, which can protect the bolt from corrosion and erosion. Generally, passivation surface treatment methods are applied to electronic products.Generally used for surface treatment of stainless steel bolts and screws.

Electrophoretic surface treatment is the use of electrophoretic technology to uniformly cover particles such as paint, latex, rubber, etc. onto the surface of bolt fasteners.After surface treatment by electrophoresis, the coating on the bolt surface is full, uniform, flat, and smooth.

Using a spray gun to evenly spray a thin layer of colored paint on the bolt fasteners has a certain anti rust effect. The most commonly used method is to spray paint on the head of the external hexagonal drill tail screw, which can effectively resist the erosion of rainwater when installed on the roof.