A Predictive Electrochemical Model for Weld Metal Hydrogen Pickup in
Underwater Wet Welding
A Predictive Electrochemical Model for Weld Metal Hydrogen Pickup in
Underwater Wet Welding
Introduction
Underwater wet welds pick up hydrogen from the surrounding water.
Hydrogen is detrimental to weld metal integrity because of HAZ cracking
and weld metal microfissuring.
Methods to minimize hydrogen pickup include flux composition modification
and hydrogen gattering.
Oxidizing fluxes with adjusted CaO/SiO2
(Basicity) ratios used in this work to reduce hydrogen pickup.
Electrochemical reactions determine hydrogen pickup in underwater wet
welds.
Optimized fluxes minimized wet weld hydrogen pickup, lowering its level
to an astonishing 13 ml/100g
Slag hydrogen content reflected similar behavior of hydrogen reduction
with FeO addition to the flux
Effect of DCEP & DCEN (polarity) on hydrogen pickup indicating the
influence of electrochemical reactions
Direct correlation between weld metal hydrogen and slag hydrogen content
Electrochemical model of hydrogen pickup as a function of partial
pressure of water vapor and activity of FeO n the slag
Conclusions
Both weld metal hydrogen content and slag hydrogen content were dependent
on the phases present in the slag.
Mössbauer spectroscopy indicated that Fe+2 was the only valence state
present in the slag for the entire range of hematite additions in the
electrode coating.
Minimum hydrogen (13.2 ml/100g) was obtained with the presence of fayalite
(2FeO.SiO2) in the slag.
Lower weld metal hydrogen contents were obtained using DCEN
(CC-) in wet welding.
Hydrogen was transported through the slag in the form of OH- ion and the
amount of OH- ions present in the slag determined the weld metal hydrogen
content. (Not demonstrated in the 5 figures presented here)
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Last modified: March 31, 2000
