Why Do Stainless Steel Centrifugal Pumps Also Rust?

Jun 26, 2025

Many users have purchased stainless steel centrifugal pumps, but after installation and use for a period of time, they feel that the centrifugal pump has rusted, thinking that the product is made of fake stainless steel material.

In fact, stainless steel centrifugal pumps rely on a very thin, strong, and stable chromium rich oxide film (protective film) formed on their surface to prevent the continued infiltration and oxidation of oxygen atoms, thus obtaining the ability to resist corrosion. Once for some reason, this thin film is continuously damaged, oxygen atoms in air or liquid will continuously infiltrate, or iron atoms in metal will continuously separate, forming loose iron oxide, and the metal surface will also be continuously corroded.

This kind of surface facial mask is damaged in many ways, and the following types are common in daily life:

 

1. The surface of stainless steel centrifugal pumps is covered with dust or foreign metal particles containing other metal elements. In humid air, the condensed water between the attachments and stainless steel forms a micro battery, triggering an electrochemical reaction that damages the protective film, known as electrochemical corrosion.

2. Organic substances such as vegetables, noodle soup, phlegm, etc. adhere to the surface of stainless steel centrifugal pumps, forming organic acids in the presence of water and oxygen. Over time, these organic acids can corrode the metal surface.

 

3. The surface of stainless steel centrifugal pumps adheres to substances containing acids, alkalis, and salts (such as alkali water and lime water splashes from decoration walls), causing local corrosion.

4. In polluted air (such as atmosphere containing a large amount of sulfides, carbon oxides, and nitrogen oxides), encountering condensed water can form sulfuric acid, nitric acid, and acetic acid droplets, causing chemical corrosion.

All of the above situations can cause damage to the surface protective film of stainless steel centrifugal pumps, leading to corrosion.

So, to ensure that the metal surface is permanently bright and not corroded, it is recommended that users:

1. It is necessary to regularly clean and scrub the surface of decorative stainless steel to remove attachments and eliminate external factors that may cause decoration.

2. The coastal area should use 316 stainless steel, which can resist seawater corrosion.

3. Some stainless steel pipes on the market do not meet the corresponding standards for chemical composition and cannot meet the requirements of 304 material.