Discolouration on a stainless weld
Stainless steel is renowned for its sleek appearance and corrosion resistance. But if you’ve ever worked with it – especially during welding – you’ve likely noticed discolouration along the welds. This actually signals a problem beneath the surface. In this post, we break down what causes stainless steel weld discolouration, what it means, and how to deal with it.
Why do stainless steel welds discolour?
When stainless steel is exposed to high heat – typically during welding – its surface chemistry changes. The chromium layer at its surface, that gives stainless its typical ‘stainless’ properties, is broken down, forming an oxide layer that produces visible colour changes. This is often referred to as ‘heat tint’.
The colour and intensity of this discolouration depend on:
–Welding temperature
-Amount of oxygen present
-Duration of exposure
-Grade of stainless steel used
Is discolouration just cosmetic?
No – this is more than a visual issue. The oxide layer that causes discolouration can reduce the corrosion resistance of stainless steel. This is because:
-The chromium content is depleted at the weld surface
-The protective passive layer is compromised
-This area becomes a weak point for corrosion, especially in aggressive environments like marine, food processing, or chemical industries
Weldbrush Electrolytic Weld Cleaning Machine
How to treat discolouration:
Many try to remove the burn mark via abrasives – these will temporarily remove it, but will actually cut deeper into the stainless surface, which creates the same problem – an opening to corrosion and contaminants.
Another method is pickling paste, which consists of leaving a strong nitric or hydrofluoric acid on the surface of the stainless. This will eventually remove the burn mark – however, again, it will not re-passivate it, and is a very dangerous process.
The most efficient method:
Use an electrolytic weld cleaner, such as a Weldbrush, which reacts with weld cleaning fluid to clean and remove discolouration from stainless welds in seconds.
This post was written and brought you by Stainless Finishing Solutions Ltd.
Stainless steel is widely valued for its strength, durability, and corrosion resistance. From food processing equipment and pharmaceutical vessels to aerospace components and architectural features,
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