The Difference Between AC and DC Welding

There are a lot of different acronyms in the welding Industry. TIG, MIG, SMAW, AC, and DC are just a few that are commonly thrown around. So, aside from the first letter of their acronyms, what’s the difference between AC and DC welding? Whether you’re working in a large facility or an at-home workstation, it’s important to know the distinguishing factors between the two.

Direction of Electricity Flow

DC stands for “direct current” and AC stands for “alternating current.” The names are a signifier of the direction in which the electricity flows. DC welding involves an electrical current flowing in one constant direction. DC also has the ability to function with a negative or positive polarity. DC-positive polarity provides more penetration than DC-negative; however, DC-negative provides a higher deposition rate.

AC differs because, whereas DC flows in a constant direction, AC can switch directions, thus also reversing the voltage with ease. The polarity of alternating currents can cycle back and forth as often as 120 times per second.

Applications

AC is typically the second choice for most welding practices because DC results in a more stable arc, smoother weld, and less spatter throughout the whole process. Situations in which DC welding is useful include stick welding, stainless steel TIG welding, overhead and vertical welding, and welding involving thin sheet metal.

However, DC can’t complete every task. For instance, DC isn’t a viable option when welding together magnetic metals. AC, on the other hand, can do this. As mentioned before, while AC is typically the second choice for welders, it’s the optimal method for aluminum TIG welding and working with metals that have a magnetized field. Although it’s great for these scenarios, it does create more spatter, produce a less stable arc, resulting in a less smooth weld.

As you can see, the difference between AC and DC welding is important to know. If you’re working with materials that have a magnetized field, you want to be sure you’re doing it the right way. Not only do you need the right knowledge, you need the right gear to help you through it as well. At Welding for Less, we have a wide collection of welding safety equipment, such as welding gloves and auto-darkening helmets, for you to use during your next task.