Golden colour in bead
Golden colour in bead
(OP)
Hi all, i have welded SS 304 with SMAW and using 308L-17 electrode.Resulting bead looks like as i have shown in the attached image. I am confused in understanding why golden and some other colors are appearing in the bead? What is the reason behind this?
Any response will be highly acknowledged.
Any response will be highly acknowledged.





RE: Golden colour in bead
On the weld it is not a concern, but on base metal (known as 'heat tint'), it's a different matter and must be removed, mechanically followed by chemically.
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Golden colour in bead
RE: Golden colour in bead
RE: Golden colour in bead
If the root surface is not protected, it will be exposed to air while it is still very hot and it will appear to be black and crusty. Again, it is simply oxidized metal, i.e., chromium, nickel, iron, etc. Welders sometimes assume it is "carbon that has been burned out of the metal". Not the case. It is simply oxidized metal.
While the mechanical properties of the base metal are not affected, the corrosion resistance is affected. Thus any oxidized material should be removed if it is used in an aggressive wetted environment.
Best regards - Al
RE: Golden colour in bead
RE: Golden colour in bead
Best regards - Al
RE: Golden colour in bead
The clear or shinny colors are when the oxide is thin enough to be transparent. The color itself is from the thickness of the film (diffraction). When the color gets dull it is thicker.
Remove it by using a clean flap wheel followed by some pickling paste (RedOne).
This is damaging for two reasons. the oxide acts like a surface contaminate and forms a crevice which is much worse from the corrosion standpoint.
The other reason is that the Cr in the oxide came from the alloy, so there is a thin layer of metal under the oxide that is significantly depleted in Cr.
Combine these two and welds (and HAZs) with any discoloration in SS are much more susceptible to corrosion than the clean surface is.
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P.E. Metallurgy, Plymouth Tube