The Effect of Hydrogen in Welding Consumables

Common welding techniques, including gas metal arc welding (GMAW) and gas-shielded flux core arc welding (FCAW-G), use consumable electrodes to conduct heat through work pieces. The hydrogen input to the weld material from the electrode is an issue, because hydrogen can create a phenomenon known as hydrogen-assisted cracking (HAC).

Electrodes

Cellulosic welding electrodes -- electrodes coated with cellulose -- have high moisture content and cause correspondingly high hydrogen input. Special measures, including observation of the correct interpass temperature -- the temperature of weld material before each pass of a multiple pass weld -- must be taken to avoid HAC if this type of electrode is used.

Steel

HAC can be a problem in pressure vessels, pipelines and other steel structures where heavy gauge steel pipe work is used. Unalloyed or low alloyed steels are particularly susceptible.

Codes

Welding codes specify various methods by which the risk of HAC can be reduced. The proper selection, handling and control of consumables are, however, the most critical factors.

References

• AWS: Effects of Welding Parameters and Electrode Atmospheric Exposure on the Diffusible Hydrogen Content of Gas Shielded Flux Cored Arc Welds
• offshore-technology.com: The Dangers of Hydrogen