What are the common surface treatments of screws
The use of screws in our life is very common, many people will be curious about the screw surface color is how to come, the screw is in the process of forming a covering layer on the surface of the workpiece, its purpose is to give the product surface beautiful, anti-corrosion role.
General screw surface treatment is mostly for electroplating, such as zinc plating, nickel plating, chrome plating, black and so on.
Galvanized, the appearance of the passivation liquid and show different colors, coating hardness is low, in the air or wet water vapor also has a good rust prevention ability, but easily soluble in acid and alkali, decoration marble dry hanging screws and nuts are generally galvanized.
Nickel plating, white appearance, magnetic, at room temperature for water and air are very stable, easy to dissolve in dilute acid, and strong alkali does not occur, and has a good decorative effect. Nickel-plated screws are also used where the coffee pot does not accept steam.
Chrome plating, the appearance is silver white, passivation ability in the air, can maintain luster for a long time, chrome plating layer has high hardness and excellent abrasion, but the cost is higher.
Blackening is generally done by chemical or electrochemical methods. At present, alkaline chemical oxidation method is used in production to improve corrosion resistance. Due to the characteristics of the appearance of the oxide film, it can only be used in general or oily media, or to take into account the effect of the appearance, the screws will be blackened.