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Metal corrosion is widespread in production and daily life; understanding it can help us reduce production costs and improve efficiency. To be victorious in every battle, one must know both oneself and the enemy. Come and take a look – various types of corrosion have been summarized here for you, which will surely be helpful to you. There are many different types of corrosion in life, and each type can be classified based on the chemical changes that occur in the metal. The following are 9 common types of corrosion: http://www.51fangfu.com/attachment/Mon_1804/2_20475_f765589ad5ea3f4.jpg?48 1. General attack corrosion, also known as uniform attack corrosion, is the most common type of corrosion. It occurs through chemical or electrochemical reactions that cause deterioration of the corrosion on the entire exposed surface of the metal. Ultimately, metal corrosion deteriorates it into scrap. General attack corrosion accounts for the largest proportion of the metal that is damaged by corrosion, yet it is still considered safe because it is predictable and can often be prevented. 2. Local corrosion: Unlike general attack corrosion, local corrosion affects only a specific area of the metal structure. Local corrosion is generally divided into three categories: (1) pitting: When a small hole or cavity forms inside the metal, pitting results in the passivation of a small area. This area becomes the anode, while the remaining metal parts become the cathode, thereby generating local electrochemical reactions. The degradation in this small area can spread throughout the entire metal, potentially rendering it waste. This form of corrosion is often difficult to detect because it usually occurs in relatively small areas and may be concealed by the compounds formed as a result of corrosion. (2) Crevice corrosion: Similar to pitting, crevice corrosion occurs at specific locations. This type of corrosion is usually associated with the microenvironment in which it occurs, such as beneath gaskets, washers, and clamps. Both acidic conditions and high oxygen levels in crevices can lead to crevice corrosion. (3) Filamentary corrosion: When water damages the coating, filamentary corrosion occurs beneath the coating or the electroplated surface. It starts as small defects within the coating and gradually spreads throughout, leading to structural defects. 3. Electrochemical corrosion: Different from ordinary metal corrosion, electrochemical corrosion occurs when two different metals are placed in a corrosive electrolyte at the same time. One of the metals acts as the anode, while the other acts as the cathode; an electrochemical cell is formed between the two metals. The anode, also known as the sacrificial metal, corrodes and deteriorates at a faster rate than when it is corroded on its own, while the cathode deteriorates more slowly compared to other methods. Three essential conditions for electrochemical corrosion to occur: (1) An electrochemical reaction must exist between metals of different types ； (2) There must be electrical contact points between the metals ； (3) The metals must be exposed to the same electrolyte. 4. Environmental corrosion: Environmental corrosion is a corrosion process in which the combined effects of various environmental conditions affect the properties of metals. Chemistry, temperature, and pressure-related conditions can lead to the following types of environmental corrosion: (1) Stress Corrosion Cracking (SCC), (2) Corrosion Fatigue, (3) Hydrogen-Induced Cracking, (4) Liquid Metal Embrittlement. 5. Flow-Assisted Corrosion (FAC): Flow-assisted corrosion, also known as flow-accelerated corrosion, occurs when the protective layer on the metal surface covered with oxides is dissolved or removed by wind or water, exposing the underlying metal layer and thereby causing further corrosion and deterioration. 6. Intergranular corrosion is a chemical or electrochemical attack that occurs at the grain boundaries of metals. The reason is that within the metal, the impurity content is often higher than near the grain boundaries, causing these boundaries to be more susceptible to corrosion compared to the interior of the metal. 7. Dealloying. Dealloying, or selective leaching, is the selective corrosion of specific elements in an alloy. The most common type of degallization is the zinc loss from unstable brasses. In this case, the result of corrosion is the deterioration and porosity of the copper material. 8. Friction corrosion occurs as a result of repeated friction, contact, and/or vibration on a rough surface, which leads to corrosion in the form of pits and grooves on the material’s surface. Fretting corrosion usually occurs during mechanical rotation and impact, when assembling bolts and bearings, as well as on vibrating surfaces exposed to external forces during transportation. 9. High-temperature corrosion: Fuels used in machinery such as gas turbines and diesel engines contain vanadium or sulfates, which can form low-melting-point compounds during combustion. These compounds are highly corrosive to metal alloys that are normally both heat-resistant and corrosion-resistant, including stainless steel. High-temperature corrosion can also be caused by high-temperature oxidation, sulfidation, and carburization.