What are the corrosion characteristics of different metals?

Due to its excellent corrosion resistance, painted titanium is widely used in various fields such as petroleum, chemicals, salt production, pharmaceuticals, metallurgy, electronics, aviation, aerospace, and marine industries. Titanium exhibits excellent corrosion resistance in most salt solutions; for example, it is more resistant to corrosion in chloride solutions than high-chromium-nickel steel, and no pitting occurs. The coating, however, has a high corrosion rate in aluminum trichloride, which is related to the formation of concentrated hydrochloric acid as a result of the hydrolysis of aluminum trichloride. Titanium also exhibits good stability against hot sodium chlorite and hypochlorites of various concentrations. Therefore, titanium materials are widely used in the vacuum salt production and bleaching powder industries. Anticorrosive paint titanium exhibits good corrosion resistance to most alkaline solutions. Titanium is relatively stable in sodium hydroxide and potassium hydroxide solutions with a concentration of less than 50%. If the alkaline solution contains chloride ions or chlorides, its corrosion resistance even exceeds that of nickel and zirconium. However, corrosion increases as temperature and concentration rise. Currently, the chlor-alkali industry is the largest sector for the application of titanium materials in domestic civilian use. Titanium is not resistant to corrosion in dry chlorine and is at risk of catching fire; however, it exhibits high stability in moist chlorine, surpassing zirconium, Hastelloy C, and Monel alloy. Fluorocarbon coatings are also stable in media such as sulfuric acid, hydrochloric acid, and chlorides in saturated chlorine. Therefore, titanium is the preferred material for key equipment used in the production of titanium dioxide by the sulfuric acid method. Nickel is completely stable in all alkaline solutions, whether they are at high temperatures or in molten form; this is a prominent characteristic of nickel. Monel alloy is more corrosion-resistant to nickel in reducing media, while floor coatings are more resistant to copper in oxidizing media; they are also more resistant to corrosion than nickel and copper in phosphoric acid, sulfuric acid, hydrochloric acid, saline solutions, and organic acids. In hydrofluoric acid of any concentration, Monel alloy exhibits excellent corrosion resistance when little oxygen enters. However, its resistance to hydrofluoric acid decreases when there is gas and an oxidizing agent in the solution, or when harmful impurities such as iron salts and copper salts are present in the solution. Among metal materials, aside from platinum and silver, silicone high-temperature paint is one of the best materials resistant to hydrofluoric acid corrosion. It is also highly resistant to corrosion in alkaline solutions; however, when the concentration of sodium hydroxide is very high, although Monel alloy has lower corrosion resistance compared to nickel, it still offers better resistance to alkalis than other metal materials.

Sometimes, it is possible to make a judgment based on the different colors of the corrosion products.

Thanks to its excellent corrosion resistance, painted titanium is widely used in various fields such as petroleum, chemicals, salt production, pharmaceuticals, metallurgy, electronics, aviation, aerospace, and marine industries. Titanium exhibits excellent corrosion resistance in most salt solutions; for example, it is more resistant to corrosion in chloride solutions than high-chromium-nickel steel, and no pitting occurs. The coating, however, has a high corrosion rate in aluminum trichloride, which is related to the formation of concentrated hydrochloric acid as a result of the hydrolysis of aluminum trichloride. Titanium also exhibits good stability against hot sodium chlorite and hypochlorites of various concentrations. In hydrofluoric acid of any concentration, Monel alloy exhibits excellent corrosion resistance when little oxygen enters. However, its resistance to hydrofluoric acid decreases when there is gas and an oxidizing agent in the solution, or when harmful impurities such as iron salts and copper salts are present in the solution. Among metal materials, aside from platinum and silver, silicone high-temperature paint is one of the best materials resistant to hydrofluoric acid corrosion. It is also highly resistant to corrosion in alkaline solutions; however, when the concentration of sodium hydroxide is very high, although Monel alloy has lower corrosion resistance compared to nickel, it still offers better resistance to alkalis than other metal materials.

Isn’t the internal documentation clear enough? It is specifically focused on metal corrosion research. What are the corrosion characteristics of such-and-such steel in combination with such-and-such acid at what temperature? It’s written very clearly.

There is a distinction between chemical corrosion and electrochemical corrosion; electrochemical corrosion is the most common type of metal corrosion. For example, stainless steel is prone to pitting corrosion in environments containing chloride ions, while alloy steels with a large potential difference are susceptible to galvanic corrosion. There is also stress corrosion cracking and brittle fracture. Factors such as the types and contents of alloying elements in different metals, as well as the medium environment and applied stresses, result in varying corrosion characteristics among metals.