Causes of corrosion in physics laboratory equipment
Physical laboratory equipment is the most common equipment problem in the use of teaching equipment, and leakage is mainly caused by corrosion. There are basically two types of corrosion in physical laboratory equipment: electrochemical corrosion and chemical corrosion. When the equipment is manufactured, the manual welding of the tube sheet and the tube is generally manual arc welding. There are different degrees of defects in the shape of the weld, such as depressions, pores, slag inclusion, etc., and the stress distribution of the weld is uneven. When used, the tube sheet part is generally in contact with industrial cooling water, and impurities, salts, gases, and microorganisms in the industrial cooling water will cause corrosion to the tube sheet and the weld. This is what we often call electrochemical corrosion. Studies have shown that whether industrial water is freshwater or seawater, there will be various ions and dissolved oxygen. The changes in the concentration of chloride ions and oxygen play an important role in the shape of metal corrosion.
In addition, the complexity of the metal structure also affects the corrosion morphology. Therefore, the corrosion of the weld between the tube sheet and the tube is mainly pitting and crevice corrosion. Viewed from the outside, there will be many corrosion products and deposits on the surface of the tube sheet, with pits of various sizes distributed. When seawater is used as a medium, galvanic corrosion will also occur. Chemical corrosion is the corrosion of media. Physical laboratory equipment will be corroded by chemical media when it comes in contact with various chemical media. In addition, there will be some bimetal corrosion between the heat exchanger tube sheet and the heat exchanger tube. Some tubesheets are also subject to erosion by corrosive media for a long time. Biological laboratory equipment, as well as temperature difference stress, the joint between the tube sheet and the heat exchange tube is easy to leak, resulting in failure of the heat exchanger.
In summary, the main factors for the corrosion of biological laboratory equipment are:
(1) Medium composition and concentration: The effect of concentration varies. For example, in hydrochloric acid, the higher the concentration, the more severe the corrosion. Carbon steel and stainless steel have the most severe corrosion in sulfuric acid with a concentration of about 50%, but when the concentration increases to more than 60%, the corrosion decreases sharply;
(2) Impurities: Harmful impurities include chloride ions, sulfur ions, cyanide ions, ammonia ions, etc. These impurities may cause severe corrosion in some cases;
(3) Temperature: Corrosion is a chemical reaction. For every 10 ° C increase in temperature, the corrosion rate increases about 1 to 3 times, but there are exceptions;
(4) pH value: Generally, the smaller the pH value, the greater the corrosion of the metal;
(5) Flow rate: In most cases, the greater the flow rate, the greater the corrosion.
In addition, the complexity of the metal structure also affects the corrosion morphology. Therefore, the corrosion of the weld between the tube sheet and the tube is mainly pitting and crevice corrosion. Viewed from the outside, there will be many corrosion products and deposits on the surface of the tube sheet, with pits of various sizes distributed. When seawater is used as a medium, galvanic corrosion will also occur. Chemical corrosion is the corrosion of media. Physical laboratory equipment will be corroded by chemical media when it comes in contact with various chemical media. In addition, there will be some bimetal corrosion between the heat exchanger tube sheet and the heat exchanger tube. Some tubesheets are also subject to erosion by corrosive media for a long time. Biological laboratory equipment, as well as temperature difference stress, the joint between the tube sheet and the heat exchange tube is easy to leak, resulting in failure of the heat exchanger.
In summary, the main factors for the corrosion of biological laboratory equipment are:
(1) Medium composition and concentration: The effect of concentration varies. For example, in hydrochloric acid, the higher the concentration, the more severe the corrosion. Carbon steel and stainless steel have the most severe corrosion in sulfuric acid with a concentration of about 50%, but when the concentration increases to more than 60%, the corrosion decreases sharply;
(2) Impurities: Harmful impurities include chloride ions, sulfur ions, cyanide ions, ammonia ions, etc. These impurities may cause severe corrosion in some cases;
(3) Temperature: Corrosion is a chemical reaction. For every 10 ° C increase in temperature, the corrosion rate increases about 1 to 3 times, but there are exceptions;
(4) pH value: Generally, the smaller the pH value, the greater the corrosion of the metal;
(5) Flow rate: In most cases, the greater the flow rate, the greater the corrosion.