Metal is the main material of equipment, it is often corroded by contacting with strong corrosive medium and various acids, alkali, salt, organic solvents and corrosive gases. Corrosion not only causes great loss, but also affects the service life of the equipment, and reduces the maintenance cycle of the equipment, increasing non-production time and repair costs. Corrosion makes the running, dripping and leakage of the equipment and pipelines more serious, causing a lot of losses, affecting the quality of the products, polluting the environment and endangering the health of the people.
Corrosion damage and corrosion accidents occur frequently. In addition to the spontaneous nature of the corrosion itself, it is largely due to the insufficient estimation of the harmful effects of corrosion. Due to there is not deep understanding on the importance of corrosion protection, lack of knowledge about corrosion and protection science, no corrosion protection measures are taken.
First. Raise awareness of corrosion
Corrosive substances are destroyed by chemical or chemical action.At the shallow level, corrosion is caused by the chemical and electrochemical action between the material and the environment, and the function of the material itself is damaged to a certain extent. The color, shape, mechanical properties and other various aspects of chemical machinery equipment after corrosion have different degrees of change, which causes the damage of chemical machinery equipment and the serious waste of energy and resources, makes the production cost of chemical enterprises relatively large.Therefore, it is a key problem for the chemical industry to adopt active and effective anti-corrosion measures to improve the anti-corrosion ability of chemical machinery and equipment.
Corrosion is divided into overall corrosion and local corrosion by surface morphology. Local corrosion is divided into small hole corrosion, stress corrosion cracking, crevice corrosion, galvanic corrosion, erosion corrosion and so on.
Metal corrosion can be divided into physical corrosion, chemical corrosion, electrochemical corrosion, etc, by mechanism.
Second. Anti-corrosion measures for equipment.
The current anti-corrosion technology mainly includes: development of corrosion resistant materials, surface corrosion protection technology, corrosion inhibition technology, electrochemical protection and so on.
1. Electrochemical protection
Electrochemical protection refers to the anti-corrosion technology that USES external current to change the corrosion potential of metals (including alloys) to reduce their corrosion rate. Electrochemical protection can be divided into cathodic protection and anode protection. Electrochemical protection technology has attracted extensive attention and application in the field of chemical corrosion prevention, and it is an effective and practical anti-corrosion method.
Corrosion inhibitor is a substance which can reduce the corrosion velocity of metal in corrosive medium under very low concentration. This substance can be a compound or a compound substance of several compounds. In the chemical industry, corrosion inhibitors are mainly used to prevent corrosion of industrial cooling water systems and chemical cleaning (pickling) of chemical equipment, pipes and boilers.There is also a amount used in the process corrosion inhibition of production process.
Corrosion inhibitor for industrial cooling water system. In the process of production, the application amount of industrial cooling water is very large. Corrosion causes the water quality deteriorated, consuming precious water resources. It can be seen that the corrosion prevention with corrosion inhibitor has heavy economic and social benefits.
Due to the chemical, physical or biological effect, the surface of chemical equipment, pipelines, boilers, etc,will be dirt(such as water scale, rust scale, grease, and biological scale, etc.).The process of chemically removing the dirt and restoring it to its original surface condition is called chemical cleaning.