Chemical Pump Encyclopedia

Critical metal parts, choose between electropolishing or passivation

electrolytic polishing

What is electrolytic polishing

Electrolytic polishing is a technique that combines a chemical bath and an electric current to precisely remove layers of material from the surface of a part, including contaminants and microscopic defects such as cracks, burrs and jagged edges. With electrolytic polishing, the average roughness (Ra) can be increased by up to 50%. This technique eliminates the need for additional metal finishing processes such as manual deburring, tumbling, grinding and other mechanical processes, hence the name Swiss Army Knife of metal finishing.

What is passivation

During the passivation of stainless steel parts, they are placed in a basket and immersed in a nitric or citric acid bath. Depending on the alloy, the acid concentration, temperature and time can be adjusted to effectively remove free iron and other contaminants from the surface of the part. By forming a chromium-rich passivation layer, passivation improves the corrosion resistance of the part and removes surface contamination. Often, parts are passivated in a bulk process.

Which is better for parts?

Although passivation removes free iron and contaminants from metal parts, electrolytic polishing is more suitable for parts because it offers the following broader advantages:

Electro-polishing is 30 times more effective than passivation in preventing corrosion. (See salt spray test below)

Electropolishing improves the pathogen resistance and cleanability of food and medical components by removing micro-cracks and surface defects that can cause problems with effective cleaning.

Electrolytic polishing can be used for many more metal alloys than passivation, even if the chromium and nickel content is low – this includes aluminium, nickel-titanium alloys and titanium.

Electrolytic polishing provides a bright, clean and even appearance.

Side-by-side comparison

Image 1: Side-by-side comparison. Source: Capable of electrolytic polishing Anti-corrosion

Corrosion protection

The following are the results of independent laboratory tests on eight stainless steel alloys after 24 hours and 888 hours of ASTM B-117 salt spray testing. The tests were carried out on unpolished and passivated specimens, passivated specimens and electrolytic polished specimens. Please see the results below.

ASTM B-117 salt spray testing

Image 2: Results of independent laboratory tests on eight stainless steel alloys after 888 hours and 117 hours of ASTM B-24 salt spray testing. Source: Capable of electrolytic polishing

What materials can I passivate?

What materials can I passivate?

Image 3: What materials can be passivated. Source: Able Electropolishing

Electrolytic polishing for precise, consistent and effective metal finishing

Passivation and electrolytic polishing are chemical processes used to improve the surface finish of metal parts. However, only electrolytic polishing can consistently and precisely remove surface defects and increase Ra by up to 50% on a wide range of metal alloys including stainless steel, aluminium, titanium, nickel-titanium alloys and many other metal alloys. Therefore, when it comes to critical components, don’t trust other techniques and choose electrolytic polishing as a more reliable option.

Magnetic Pumps

For efficient electrolytic polishing and pickling passivation, a wide range of chemical solutions must be used and these need to be conveyed by high quality magnetic pumps. The excellent performance and reliability of our magnetic pumps ensure precise and consistent delivery of chemical solutions, resulting in increased productivity and product quality.

Precision Chemical Filters

To ensure the effectiveness of electrolytic polishing and passivation, the purity of the chemical solution is essential. For this reason, we recommend the use of QEEHUA PUMP’s filter machines to keep the chemical solution clean. Our filters use highly efficient filtration technology to ensure the purity and stability of the solution. Let QEEHUA PUMP’s filters provide reliability for your production line!

Whether using electrolytic polishing or passivation, the chemical solutions required are corrosive. The use of QEEHUA PUMP’s magnetic pumps for the transfer of chemical solutions effectively prevents leakage and ensures a safe production environment. At the same time, in combination with a chemical filter, the chemical solution can be kept pure, further improving production efficiency and product quality.