What are the commonly used materials and corrosion-resistant treatments for long-axis pumps

Long-shaft pumps are widely used in many industries such as chemical industry, petroleum, mining, water treatment, etc., and the media they transport are diverse and complex. Material selection and corrosion resistance treatment have become key factors to ensure the stability of long-shaft pump performance and service life. Reasonable material selection and scientific treatment not only improve the durability of the pump, but also effectively reduce maintenance costs and improve operating efficiency.

Classification of common materials for long-shaft pumps
The main components of long-shaft pumps include pump shafts, impellers, pump casings, sleeves and seals. Each component uses different materials to meet performance requirements according to its different stress, wear and corrosion environment.
Carbon steel and low alloy steel
Carbon steel is often used in structural parts and load-bearing parts due to its low price and good mechanical properties. Low alloy steels such as 20Cr and 35CrMo have high strength and toughness after heat treatment, which are suitable for manufacturing shafts and connectors of long-shaft pumps. The surface of carbon steel usually needs to be treated with anti-corrosion, which is suitable for working conditions with low corrosive media.
Stainless steel materials
Stainless steel is widely used in impellers, pump casings, sleeves and other susceptible parts due to its excellent corrosion resistance. 304 stainless steel is suitable for general corrosion environments, while 316L stainless steel has stronger chloride corrosion resistance and is often used in seawater and chemical media. Ultra-low carbon stainless steel materials improve weldability and corrosion resistance and extend equipment life.
Corrosion-resistant alloys
Nickel-based alloys (such as Hastelloy C-276 and Monel 400) have excellent corrosion resistance and high temperature resistance and are suitable for acidic, high temperature and highly corrosive media transportation. Titanium alloy materials are lightweight and highly corrosion-resistant and suitable for special environments. Corrosion-resistant alloys are expensive and are mostly used in key components and harsh working conditions.
High-hardness alloys and composite materials
High-hardness alloys such as high-chromium cast iron and tungsten carbide spray coatings are used to improve the wear resistance of pump bodies and impellers. Composite materials such as polytetrafluoroethylene (PTFE) and reinforced fiber composite materials are used in seals and linings, with excellent corrosion resistance and wear resistance, extending maintenance cycles.

Long-shaft pump corrosion-resistant treatment technology
Even if long-shaft pumps use corrosion-resistant materials, they still require a variety of surface treatment technologies to further enhance corrosion resistance and prevent medium erosion and mechanical damage.
Thermal spraying technology
Thermal spraying includes plasma spraying, flame spraying and other methods to spray wear-resistant and corrosion-resistant materials onto the surface of the pump body. Commonly used spraying materials include tungsten carbide, chromium powder, and nickel-based alloys to form a dense hard coating, which significantly improves the wear and corrosion resistance of the impeller and pump casing.
Electroplating and chemical plating
Electroplating nickel and chemical nickel plating processes provide a uniform corrosion-resistant layer for pump shafts and parts, enhancing surface hardness and oxidation resistance. Chemical plating has no current and is suitable for uniform coverage of parts with complex shapes. The thickness and adhesion of the electroplating layer are critical to ensure long-term protection.
Heat treatment strengthening
The hardness and wear resistance of carbon steel and low-alloy steel are improved through heat treatment processes such as quenching and tempering. Strengthening treatments such as surface carburizing and nitriding improve the fatigue resistance and corrosion resistance of the pump shaft. The heat treatment process needs to be reasonably designed in combination with material properties and the use environment.
Anti-corrosion coating
Epoxy resin coating, polyurethane coating and fluorocarbon coating are applied to the external and internal surfaces of the pump body to form a physical isolation layer to prevent moisture and corrosive media from directly contacting the metal. High-performance anti-corrosion coatings are suitable for acid-base corrosion and seawater environments to extend the service life of the equipment.
Anodic protection technology
Sacrificial anode or electrochemical anode protection technology is used to effectively inhibit the electrochemical corrosion process on the metal surface. It is suitable for long-axis pumps to be immersed in strong corrosive media such as seawater and salt water for a long time, reducing maintenance frequency and equipment loss.

Material selection principles under different working conditions
Long-axis pump materials and treatment methods need to be comprehensively considered based on working conditions such as medium properties, temperature, pressure and mechanical load. Acidic and alkaline media, high temperature and high pressure environments, and media containing solid particles all have different requirements for material performance. Highly corrosion-resistant alloys are suitable for acidic corrosion environments, wear-resistant alloys are used for liquids containing sand particles, and composite materials meet special sealing and corrosion resistance requirements.