Choosing the correct shield gas is an important part, it plays a huge role in the welding process. The shielding gas not only protects the weld from getting contaminated from oxygen, nitrogen, or oxygen but can also affect the size, shape, fusion, speed, spatter and porosity too. In order to achieve strong, tough and corrosion-proof weld the welder should be well aware of the science behind that.

The welder needs to identify his/her goals in respect to get the better result, because no shielding gas exist which can fit in all type of welding, to choose the correct shield gas one should look into: the cost of gas, the base metal, the weld transfer process, penetration & post weld cleans ups, finished weld properties and the productivity goals.

For the Metal Inert Gas welding process, the mixture of CO2 and argon is an excellent choice, it also helps in welding thin automotive parts such as exhausts using solid wire. A mix of 2.5% carbon dioxide and argon which gives a good wetting action, produces a smooth weld with minimal spatter & low surface oxidation with relatively low fusion. 

For the pipework and paneling for components ranging from 3mm to 12mm which requires high integrity welds should consider argon, helium and CO2 mixture. It produces weld with low-temperature toughness values, low levels of porosity, high penetrations and excellent corrosion resistance. 

Here while choosing the correct shielding gas one should consider safety as a priority too because the welder is going to deal with high-pressure cylinders. It is important to purchase or rent shielding gases from a reputable company that can give an assurance that following strict standards are met and the gas cylinder complies with the regulations.