The definition of seamless steel pipes
A seamless steel pipe is a type of pipe made from a solid round steel billet, which is heated and then pushed or pulled over a form until the steel is shaped into a hollow tube. Unlike welded pipes, seamless pipes do not have any seams or joints, making them stronger and more reliable under high pressure, high temperature, and corrosive environments.
Galvanizing of seamless steel pipes
Features: Zinc is relatively stable in dry air and does not change color easily. In water and humid atmosphere, it reacts with oxygen or carbon dioxide to form an oxide or alkaline zinc carbonate film, which can prevent the zinc from continuing to oxidize and play a protective role.
Zinc is highly susceptible to corrosion in acids, alkalis, and sulfides. The galvanized layer generally undergoes passivation treatment. After passivation in chromic acid or chromate solution, the formed passivation film is not easy to interact with moist air, and the anti-corrosion ability is greatly enhanced.
For spring parts, thin-walled parts (wall thickness <0.5m) and steel parts requiring high mechanical strength, hydrogen must be removed. Copper and copper alloy parts do not need to be dehydrogenated.
For spring parts, thin-walled parts (wall thickness <0.5m) and steel parts requiring high mechanical strength, hydrogen must be removed. Copper and copper alloy parts do not need to be dehydrogenated. Galvanizing is low cost and easy to process.
Application: Galvanizing is commonly used in atmospheric conditions and other favorable environments. But it is not suitable for friction parts.
Cadmium plating of seamless steel pipes
Features: For parts in contact with marine atmosphere or seawater and in hot water above 70℃, the cadmium coating is relatively stable, has strong corrosion resistance and good lubricity. Dissolves very slowly in dilute hydrochloric acid, but is extremely soluble in nitric acid, insoluble in alkali, and its oxides are also insoluble in water. Cadmium coating is softer than zinc coating. The coating has less hydrogen embrittlement and stronger adhesion. Moreover, under certain electrolysis conditions, the resulting cadmium coating is more beautiful than zinc coating. However, the gas produced when cadmium is melted is toxic, and soluble cadmium salts are also toxic.
Under normal conditions, cadmium acts as a cathodic coating on steel, and acts as an anodic coating in marine and high-temperature atmospheres.
Application: It is mainly used to protect parts from the atmospheric corrosion of seawater or similar salt solutions and saturated seawater vapor. Many aviation, navigation and electronic industry parts, springs, and threaded parts are plated with cadmium. It can be polished, phosphated and used as a base for paint, but cannot be used as tableware.
