In the process of transportation, screws and zinc coating often appear white, black, black and other phenomena, mainly caused by zinc coating, corrosive medium and exposure of moisture, oxygen and carbon dioxide in the atmosphere.

In order to prevent this phenomenon, the surface state of the good materials that can be tried to use is before the screw processing. Due to the galvanizing process, the surface of the defective screw is easy to be penetrated by corrosive media such as acid, alkali, salt, etc., which is difficult to clean and lead to corrosion.

The reasonable selection of packaging materials avoids the use of plastic products that are not zinc. Packaging materials, such as galvanized iron sheet metal, are the best. The box can be placed in a desiccant with appropriate humidity to reduce the relative humidity compatibility and prevent the warehouse corrosion of harmful gases. At present, the so-called screw and nut metal surface treatment market longzinc (NASDAQ Stock Code rust).

In order to prevent the non-standard screws from being degreased, they are degreased, and swim on the rust preventive screws and nuts of the rust removal and rust preventive agent, or use zinc and chromium compounds to form protective films on the metal surface. Spray method is formed and dried and cooled. Then the process is repeated once, and the obtained information is about 5? 8, silver gray, based on the information thickness provided by the manufacturer of the display. Good rust and corrosion resistance.

Phosphate treatment is a kind of phosphate chemical treatment that contains metal to metal surface to form phosphate protective film phosphating treatment solution, which is insoluble in water and has excellent phosphate coating tightness. It is used as the bottom layer of its main purpose and the metal layer of cold adsorption lubricant of coating. Because phosphate coated film is composed of a series of zinc, manganese, hydrogen phosphate and iron phosphate crystals of different sizes, the film is porous, with large specific surface area, good absorption, adsorbed coating or a large number of lubricants, so it is often used as primer, or cold stamping to reduce friction and steel, cold drawing steel wire lubrication layer.

The oxidized steel parts will be immersed in the alkali treatment solution containing oxidant, such as potassium hydroxide or sodium hydroxide solution of nitric acid, and keep its boiling point at about 140 ℃, or the molten salt of nitric acid and sodium hydroxide will be immersed in the steel parts, and it is pleasant to remove the surface layer, so that the eyes with black iron oxide film in the composition with mixture of ferrous oxide and iron oxide can be cooled suddenly in water, It is a way to improve the corrosion of ferrous metals