I selected the edgeloops I wanted and extracted those as curves.
I have curveu attribute which came from resample node. (0-1 from the first point to the last for each curve). Then I transfer that on to the pipe geometry with certain radius.
This is kind of direction of the welding flow.
Next I created a noise on the curves using the curveu as position for the noise and piped that into pscale of the curvepoints. Transferred that on the pipe with VEX which reads the pscale from the curve and uses that as a radius how far the gradient goes.
And the third gradient is for the colorization which is quite wide and has some noise distort in it.
Houdini setup is fairly simple
The shader has grown a bit... I should clean the colorization... Its a huge mess right now...
colorization itself doesn´t have anything special. Main thing is the Arnold thin film node which is deprecated and I hope they will keep it. Same thing could be done in the starndard shader I believe but this way I had more control.
But this was the interesting part.