What is the burn mark on stainless steel welds? Causes and treatment
- Dana Temple
- Aug 5
- 3 min read
In this article, we'll explore the science behind burn marks, their causes, and how electrolytic weld cleaning can restore your stainless steel to its original shine.
Stainless steel is renowned for its corrosion resistance and sleek appearance, but welding it can sometimes leave behind unsightly burn marks - those dark discolorations that can compromise both aesthetics and performance. If you've worked with stainless steel, you’ve likely encountered these marks and wondered: What causes them, and how can they be effectively removed?
What is a burn mark on a stainless weld?
A burn mark is a visible discoloration that appears near or on a stainless steel weld. These marks often appear blue, brown, or black, depending on the temperature reached during welding. They’re more than just surface blemishes - they’re a sign that the protective chromium oxide layer has been damaged or burned off.
This oxide layer is what gives stainless steel its corrosion resistance. Once compromised, the metal underneath becomes more susceptible to rust and corrosion, especially in harsh environments.
What causes burn marks on stainless welds?
Burn marks are typically caused by excessive heat and inadequate shielding during the welding process. Here are the most common culprits:
Overheating the metal
Welding stainless steel at high temperatures without proper control can lead to oxidation and discoloration.
Insufficient shielding gas
If the weld isn’t properly shielded with inert gas (like argon), oxygen in the air can react with the hot metal, forming oxidized layers.
Poor torch angle or travel speed
Incorrect torch positioning or moving too slowly can concentrate heat in one area, increasing the chance of burn marks.
Contaminated work surface
Residues like oil, dirt, or other contaminants can also react during welding, contributing to burn mark formation.
Why you should remove burn marks
Beyond aesthetics, untreated burn marks can lead to:
Corrosion: The exposed area is more reactive and vulnerable to rust.
Product Failure: Especially in food-grade, pharmaceutical, or marine applications.
Regulatory Issues: Some industries require completely clean, passivated welds to meet compliance standards.
How to remove burn marks using an electrolytic weld cleaner
The most effective and environmentally friendly way to remove burn marks is through electrolytic weld cleaning. This process uses a mild acidic electrolyte solution and an electric current to clean and re-passivate the stainless steel surface.
Weldbrush is a high-performance electrolytic weld cleaner that quickly removes heat tint and discolouration without damaging the metal.
Here’s how it works:
Apply the electrolyte: The carbon fibre brush is dipped in the cleaning fluid.
Electrochemical reaction: The Weldbrush passes an electrical current through the brush, creating a safe, localised electrochemical reaction.
Removal & re-passivation: Burn marks are stripped away, and the chromium oxide layer is restored in one step.
Neutralise: A neutralising fluid is used afterward to neutralise any acid residue
Final rinse: Spray down the cleaned area with water to remove any leftover electrolyte or neutraliser residue, ensuring a clean, passive surface finish.
Benefits of Using Weldbrush:
Instant Results: Burn marks vanish within seconds.
Surface Integrity Maintained: No abrasion or grinding required.
Eco-Friendly: No harsh acids or toxic fumes.
Portable and User-Friendly: Ideal for field or workshop use.
Alternative Methods (and Why They Fall Short)
Some fabricators try to remove burn marks using:
Grinding or Sanding: This damages the surface and doesn’t restore passivation.
Pickling Paste: Effective but highly toxic, corrosive, and environmentally hazardous.
Wire Brushing: Can spread contaminants and doesn’t remove oxidation properly.
Compared to these, Weldbrush provides a faster, safer, and more professional solution. It will also re-passivate the stainless, returning it to its corrosion-resistant state - none of the alternative methods will do this.
Conclusion: Clean welds, Clean reputation. ✅
Burn marks on stainless welds aren’t just a cosmetic issue—they signal a compromised surface. Whether you're working on architectural, medical, marine, or food-grade equipment, maintaining the integrity and appearance of your welds is critical.
With an electrolytic weld cleaner like Weldbrush, you can easily remove burn marks, restore corrosion resistance, and present your craftsmanship at its best.
Need help choosing the right Weldbrush model for your application?
Contact our team or browse our range of cleaners to find your perfect match.
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