Dissociation enthalpy of shielding gases
The dissociation enthalpy of shielding gases is the energy absorbed when gas molecules split in the arc. If the enthalpy is too low, the gas cannot shield effectively.
Physicochemical mechanism of action
The dissociation enthalpy is the energy required to split multi-atomic molecules into their atomic components. In the welding arc, shielding gases such as argon or helium are split to form an effective protective layer around the workpiece.
Metallurgical relevance & risks in welding
If the dissociation enthalpy is too low, the shielding gas is not sufficiently activated and loses its protective function. This can lead to inadequate isolation of the workpiece from oxygen and other contaminants, resulting in corrosion or incomplete weld formation.
Workshop practice & action instructions
To ensure effective dissociation enthalpy, the shielding gas should be used at the right concentrations and at the correct temperature. For argon, the typical dissociation enthalpy is about 26 kJ/mol. For helium, this value is slightly higher. It is important that the gas receives sufficient activation in the arc to perform its shielding function.