Lack of Fusion after galvanization

[demsha]

Hello All;

we have noticed many lack fusion welding defects on caisson shoes after galvanization (on white metal). These defects were not detected and UT inspection was passed when these shoes were tested on black metal (before galvanizing). What type galvanization parameters could have caused these defects?

Thanks in advance
Demsha

 

[metengr]

Are you sure these are lack of fusion defects? They could be surface cracks associated or caused by hydrogen embrittlement (delayed cracking) from the welding process. Better look again.

 

[demsha]

they are not like hydrogen embrittlement cracks. Photos clearly show defects are at the fusion lines. These defects are much larger than hydrogen embrittlement cracks. I would like to show these pictures, but I cannot attach them. The system is asking link for these photos.

 

[gtaw]

Hydrogen cracking would be expected to be at the weld interface or in the HAZ. The area of the weld that is hardest is the likely area to experience hydrogen assisted cracking.

Before the member is HDG, it is subjected to a hot pickling operation that can introduce diffusible hydrogen into the area welded.

Best regards - Al

 

[ndeguy]

demsha

Your post heading "LOF after galvanisation" is erroneous if NDT (UT and MPI) was suitable prior to galvanisation.

If items were proven to be defect-free prior to galvanisation then I suggest that metengr and gtaw are likely correct and these are not LOF defects.

Of course there is always the possibility that NDT was not done suitably in which case the caisson shoes may have LOF defects.