Nickel and nickel alloys are widely used in the chemical industry due to their excellent thermodynamic stability and corrosion resistance. This article mainly introduces the corrosion resistance of several typical nickel-based alloys.
Pure nickel shows good corrosion resistance in many corrosive media due to its high chemical stability. Nickel is very corrosion-resistant in dry and humid atmospheres, and is quite stable in dilute acids such as hydrochloric acid less than 15%, sulfuric acid less than 70%, and many organic acids. However, pure nickel has poor corrosion resistance in oxidizing strong acids such as nitric acid and oxidizing environments. Nickel shows excellent corrosion resistance in alkaline media and is an ideal material for making high-temperature and strong-alkali equipment.
Nickel-chromium alloys improve corrosion resistance by adding chromium to pure nickel. Chromium is an element that is easy to passivate. Its addition can improve the passivation performance and oxidation resistance of the alloy, thereby improving the corrosion resistance of the alloy in oxidizing acids, salt solutions and oxidizing environments. It also increases strength and hardness. According to the chromium content, nickel-chromium alloys can be divided into four categories: 15-25% Cr, 30-35% Cr, about 40% Cr and about 50% Cr. The higher the Cr content, the stronger the alloy’s oxidation resistance, but its corrosion resistance decreases in reducing environments.
Nickel-molybdenum alloy is made by adding molybdenum element to improve the resistance of pure nickel to reducing acids. The addition of molybdenum moves the potential of the alloy in the positive direction, improving the corrosion resistance in hydrochloric acid and sulfuric acid media. Generally, when the molybdenum content reaches 15% or higher, the corrosion resistance improvement effect is significant, and the best effect is when the molybdenum content is 30%. Commonly used nickel-molybdenum alloys are Hastelloy A, B and B2, which have excellent corrosion resistance in hydrochloric acid and sulfuric acid media below 70°C. However, nickel-molybdenum alloys have poor oxidation resistance and poor corrosion resistance in oxidizing environments.
Nickel-chromium-molybdenum alloy combines the characteristics of nickel-chromium alloy and nickel-molybdenum alloy. It has both good oxidation resistance and excellent reduction resistance, so it shows excellent corrosion resistance in both oxidizing and reducing environments. The representative of this type of alloy is the Hastelloy C series, which achieves a wide range of corrosion resistance through the optimal ratio of Cr, Mo and other alloying elements.
In the chemical industry, acids, alkalis, oxidizing and reducing environments widely exist. Selecting appropriate corrosion-resistant materials is key to designing chemical equipment. Nickel and nickel alloys have become the materials of choice in these environments due to their excellent corrosion resistance and thermodynamic stability. This article introduces several typical nickel-based alloys and their corrosion resistance properties in detail, which can provide a reference for the selection of chemical equipment.
In future research, the development direction of nickel-based corrosion-resistant alloys is:
1) Develop high alloying alloys with higher contents of Cr and Mo to expand their application temperature range;
2) Add more alloy elements such as W, Nb, etc. to obtain wider corrosion resistance;
3) Develop higher strength alloys;
4) Study the corrosion mechanism and protection methods of this type of alloy, and develop more environmentally friendly composite materials as alternative materials.
Tianjin Anton Metal Manufacture Co., Ltd. is a company specializing in the production of various nickel-based alloys, Hastelloy alloys and high-temperature alloy materials. The company was established in 1989 with a registered capital of 10.0 million, specializing in the production and sales of alloy materials. Anton Metal’s products are widely used in aerospace, chemical industry, electric power, automobile, nuclear energy and other fields, and can also provide customized alloy material solutions according to customer needs. If you need to know the price consultation of alloy materials or provide customized alloy material solutions, please feel free to contact the sales staff.
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Post time: Apr-24-2024
