Cleaning welds on stainless steel – Comparison of four proven methods

Many do-it-yourself welding enthusiasts and professionals working with stainless steel, know that the metal is painted as it is a heating and welding process. This can spoil the aesthetic appearance of the finished project and make it amateurish.

That’s why many welders want to know how to clean stainless steel after welding.

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The best way to clean stainless steel after welding is electropolishing. In this process, the acidic electrolyte on the metal surface is oxidized by electricity.

Electropolishing not only cleans the surface from stains but also contributes to the correct passivation of the metal. This coats the surface with a layer of urchin chromium oxide, giving it the luster that stainless steel is known for.

Why clean stainless steel welds?

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The weld cleaning process is carried out to improve the corrosion resistance of metal surfaces after TIG, MIG, and other types of welding.

Metal surfaces and welds are very susceptible to various types of wear – rust and cross-contamination are just a few examples.

After using certain welding processes, problems such as discoloration and heat marks are common.

Both types of issues can be fixed with the right cleaning and finishing.

What are heat shading and corrosion?

Thermal shades

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Most metals, including stainless steel, have an oxide layer on the surface. Thermal painting thickens this natural oxide layer and causes the color change. When light is reflected from a metal surface, moderate colors are a direct result of light interference effects.

Light reflected from the normal surface of the oxide layer and light reflected from the oxide-metal interface created by welding produce different colors depending on the thickness of the oxide layer.

Various terms are used in the welding industry to describe this phenomenon, such as color change, oxide deposits, and rainbow effect. All these terms mean the same thing, discoloration of the top layer of stainless steel. This usually occurs around the boil and in an area that is exposed to heat.

Types of weld cleaning

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There are three weld cleaning methods for removing burnt paint from a stainless steel TIG weld:

  • mechanical method
  • chemical method
  • electrochemical method

All four methods make sense in different situations, but they all work more or less according to the same principle: the passive layer destroyed by the arc heat during welding is restored. To understand exactly what’s happening here, we need to quickly peek beneath the surface of the stainless steel.

1. Mechanical weld cleaning

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Mechanical weld cleaning is inexpensive. For small problems, mechanical cleaning stainless steel welds methods are usually quite useful. Rust deposits on stainless steel surfaces can be easily removed with these methods. Use the following method to pure stainless steel.

After welding, the remaining rust on the stainless steel must be removed. Rust is no more difficult to cut than stainless steel.

There are three things to do at this point, so keep this in mind when sanding. First, roughen the surface of the stainless steel to make rust removal easier. Second, a grinder should be used to grind rust. In third place is the use of lubricants to prevent corrosion. It is used to achieve a beautiful finish on stainless steel surfaces.

Welds on the steel surface can be easily cleaned thanks to the sandblasting process. Sandblasting is performed by forcing air under high pressure through the nozzle. Rust is removed when high-pressure air is suddenly introduced into the welding area.

2. Chemical weld cleaning

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Chemical weld cleaning is the most common method of cleaning metal. This includes the use of a chemical pickling paste for post-fermentation cleaning. The paste is applied with a brush or spray to the damaged areas and is left on the surface for some time to interact with the metal. It is later removed, and the surface is neutralized with a neutralizing agent.

This chemical cleaning stainless steel welds process is effective enough for cleaning steel after fabrication, but welders dislike it for a number of reasons.

First, chemical pickling paste contains various toxic acids such as hydrofluoric acid, nitric acid, and sulfuric acid. These chemicals are very dangerous to the human body and can cause serious long-term damage to the skin and internal organs if swallowed or inhaled.

Second, only a certified operator may use chemical pickling paste. The operator’s body must be fully covered to avoid contact with acid. That is why pickling is usually only used in commercial workshops and automated operations.

3. Electrochemical weld cleaning

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Electrochemical weld cleaning is faster and more efficient than the other two methods. It also does not pose a significant risk to human health.

This electrochemical weld cleaning method is exceptionally effective at removing cross-contamination, rust, and other contaminants from metal surfaces and always produces a clean weld.

The electrochemical weld cleaning process is very simple.

A mild electrolytic cleaning fluid is applied to the surface of the weld with a conductive weld cleaning brush. Electric current (AC/DC) is applied so that the desired cleaning and passivation results are achieved.

Electrolytic weld cleaning

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This method cleans the seams with a conductive carbon fiber brush. This technique is quick and easy. A cleaning solution for welding is applied to the workpiece with a brush. At the same time, an electrical current (AC/DC) is present. Welding is now simplified. Below is a discussion of some of its unique features.

You don’t need to clean welded steel if that’s important. You can take a cleaning brush with you there.

Rust on stainless steel can only be removed with pickling paste and this conductive seam cleaning brush. There are no extra steps.

Only welded steel areas should be cleaned. This will make you more focused and precise.

If these methods are used to clean the weld, contamination of the steel can be avoided. In addition, this process stops the corrosion of the steel surface.

Rust point

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Stainless steel has a rougher surface structure in the tempering color and is therefore more corrosive. In other words, stainless steel, which should resist rusting, may begin to rust where the passive coating has been removed.

In addition, the rough surface of baked paint is an ideal breeding ground for microbes. This is particularly problematic for applications where the highest hygiene requirements are imposed, such as in the healthcare or food industry.

Advantages of electrochemical cleaning

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Both electrochemical methods can be used to pure stainless steel after welding. Each of them offers different advantages to the welder.

Flexibility and ease of use

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Electrochemical cleaning can be easily carried out anywhere, as the device is portable and easy to carry. You can perform manual electrochemical weld cleaning with a brush on-site, off-site, and anywhere else.

Electrochemical cleaning is also effective for all types of welded joints, including seam and surface.

Application security

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Electrolyte fluids do not contain dangerous chemicals such as pickle paste. It contains only mild phosphoric acid, which is also found in regular soft drinks. The primary interacting agent is electricity, not the electrolyte chemical itself.

This makes electropolishing very safe and can be used by both amateurs and professionals. Although you will need some protective equipment, such as gloves and an apron, to stay clean, high-impact suits are not required for electrolytic cleaning.

Application speed

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The electrochemical weld cleaning process does not take much time. If you have the equipment ready, it will take half an hour to clean the entire workpiece from edge to edge.

A good electropolishing machine will both clean and passivate the metal surface at the same time, and you won’t have to repeat yourself.

Optimal corrosion resistance

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Mechanical weld cleaning and even chemical cleaning do not protect the metal from future corrosion. Studies of welding equipment have shown that the electrochemical process provides the best corrosion resistance compared to other cleaning processes due to the passivation effect.

Which equipment is best for grinding welds?

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Essentially, each of the four approaches has the following advantages:

  • Some automated manufacturing processes are useful for chemical cleaning or etching welds. The disadvantage of this process is that the brine is expensive and harmful to people and the environment.
  • Inexpensive stainless steel brushes or rags are advantageous for mechanical weld cleaning seams. The disadvantages include that it takes time and is not always reliable.
  • Even outside of buildings, the electrochemical cleaning of stainless steel welds is quick, easy, and thorough. Passivation and temper colors are removed in one step. However, you should have the right tool for cleaning welds on hand.

What makes a good weld cleaner?

If you are interested in professional electrochemical weld cleaning, several vital factors and properties should be considered when choosing the right device:

  • Well-proven supplier know-how in welding technology
  • Simple, clear control
  • Ready to use in just a few steps
  • Economical use of liquid electrolytes / simple and accurate dosing
  • Low-power consumption
  • Robust product body with the lowest possible weight
  • Quality accessories for different purposes
  • Easily accessible and/or regional sales and service network

After cleaning, the polishing process ensures that the stainless steel surface has an even shine.

FAQ

How do you clean stainless steel welds?

The best way to clean stainless steel after welding is through a process called electropolishing. In this process, an acidic electrolyte is oxidized on the metal surface using electricity.

Do you need to clean stainless steel welds?

First, it just looks better. And secondly – and this is the real highlight – correct weld cleaning seams prevent corrosion, i.e., the long-term degradation of the stainless steel.

What acid is used to clean stainless steel welds?

Pickling pastes contain a combination of hydrofluoric acid and nitric acid that can cause severe burns. They are mainly used for re-welding clean stainless steel and can be applied with a brush or by spraying.

What to use to clean up welds?

The most common product used to chemically clean welds is “pickle paste”. It is very effective in removing surface contamination including rust, stains, and heat discoloration from metals. At first glance, pickle paste may appear to be quite easy to use.

How do I remove discoloration from stainless steel?

During the welding process, stainless steel is heated to very high temperatures, which causes the metals to take on different colors, such as gold, red, purple, blue, or brown, depending on the temperature. Although these colors look beautiful, they reduce the composition and oxidation properties of stainless steel.
There are several methods for removing discoloration from stainless steel after welding. The most common are electrochemical cleaning, chemical pickling, mechanical grinding, and brushing.

How do you clean up after welding?

Chemical cleaning is the most common metal cleaning method. It involves the use of a chemical pickling paste for post-weld cleaning.
The putty is applied with a brush or sprayer to the damaged areas and left on the surface for some time to interact with the metal.

Conclusion

When cleaning stainless steel after welding, the correct processes can be followed quickly. In addition to cleaning, stainless steel also needs to be polished.

The hardness, durability, and shine of this steel are its main characteristics. Electrochemical methods are the most acceptable for maintaining the pristine finish and brilliant shine of stainless steel.

When cleaning the stainless steel surface after welding, you must also ensure that the surface layer is repaired.

Aron Russell

If you have come to my page, then you are trying to learn the correct technique for welding various parts. I can confidently say that you can trust me. I have been studying multiple welding techniques for 20 years. In my youth, I got a job at a factory, where my acquaintance with this technique began.

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