AC Vs. DC Welding – Learn the Differences (With Pros & Cons)

DC ( Direct Current) and AC (Alternating Current) are the two power sources utilized for welding jobs. However, DC is best suited for most welding tasks. But AC has its own importance when welding delicate metals such as aluminum.

Sometimes understanding welding current and polarities is quite challenging for novice and experienced welders because of the many variations in electric current.

Read the blog below to understand the differences between AC & DC welding.

The Difference Between AC and DC Welding

The main difference between AC and DC welding is the flow of polarity; in AC, it changes every second. On the other hand, in DC welding, polarity flows in a single direction.

DC is the recommended powered source for most welding tasks, as the polarity flows in a single direction providing a stable arc. On the other hand, AC cannot produce stable arc when stick welding because the polarity changes every second.

Polarity is so important when it comes to welding because the strength and quality of the weld are directly proportional to the polarity of the current.

Key differences between AC and DC welding
Key Differences Between AC and DC Welding

What is AC Welding?

When AC welding, the electric current changes its direction repeatedly by moving back and forth. Polarity is changed 120 times per second with a 60-hertz current. Besides, arc deflection does not exist in AC welding, as it fastly reverses the current direction and magnetic field.

Welders are not required to do any modification when AC welding, as its compatible with the standard power source provided to domestic outlets.

Advantages of AC Welding

  • The voltage doesn’t drop when using long cords, unlike DC. This helps to perform welding operations smoothly when the power source is away.
  • AC stick welding machines are cheaper, but they are obsolete nowadays.
  • DCEP phase in AC allows TIG to weld aluminum and magnesium remarkably.
  • AC output aids in welding metal that could be affected by the magnetic field, producing a stable arc, which helps eliminate arc deflection and arc blow.
  • AC is best suited for stick welding special electrodes, provided these are available.

Disadvantages of AC Welding

  • AC is not suited for welding stainless and mild steel, as it produces a less stable arc that creates spatters.
  • The welds from stick welders are not high quality as DC output.
  • AC TIG welders cost more than DC TIG welders.

What is DC Welding

When DC welding, the current flows in a single direction, and polarity remains constant. Continuous electricity flow is required, so you will use a ground clamp and a welding gun to complete the electric circuit.

As the polarity is either positive or negative in DC welding, you must ensure to choose the right polarity, as choosing the wrong could lead to a weak joint. Ensure the proper connection of ground clamps and welding gun with your machine. Polarities changes for each metal being welded and electrode type.

DC welding creates a stable arc, as the magnetic field and current arc remain constant.

DCEP(Direct Current Electrode Positive)

In DCEP, you will plug in the electrode cable in the positive terminal of the welding machine and connect the ground clamp with the negative terminal. 70 percent heat is placed on the electrode and 30% on the workpiece.

DCEP
Reverse Polarity DCEP (DC+)

DCEN (Direct Current Electrode Negative)

In DCEN, you will connect the electrode cable to the negative terminal and the ground clamp with the positive terminal. Work receives 70% heat, while the electrode receives the remaining 30%.

DCEN
Straight Polarity DCEN (DC-)

DCEN is referred to as straight polarity, as the electron travels from a negative to a positive point. For instance, if the electrode is connected with the negative terminal, then electrons flow from the electrode to the workpiece and vice versa.

Advantages of Using DC Welding

  • DC output produces a more stable arc than AC when stick welding, leading to uniformity in weld shape.
  • A stable arc helps produce welds with less spatter.
  • Offers greater arc deposition
  • DCEP helps in deeper penetration when stick welding.
  • DCEN provides a rapid filler deposition rate. However, it does not offer deep penetration, which creates problems welding thinner gauge metals.
  • DC welders are less expensive than AC welders.
  • Welds a vast variety of metals.

Disadvantages of Using DC Welding

  • TIG welders with DC modes cant weld aluminum.
  • The equipment required to work with DC welders costs you more.
  • Magnetic arc blow and deflections are challenging

Applications of AC and DC Welding

AC TIG welding helps in welding delicate metals like aluminum. Contrarily DC is the jack of all trades.

AC Welding: It helps in the shipping industry, where seam welds are required, as it generates more current than DC. Besides, it also offers a rapid filling rate and can be used to weld heavy plates.

Adding more to it, switching to AC positive aids in eliminating the oxide layer from the metal surface, which makes it capable of welding aluminum. It can weld metals with magnetic properties, making it suitable for repairing machinery.

Ac welding is the best option when welding away from the power source.

DC Welding: It is most suited for vertical and overhead welding positions.Its the best option for welding metals such as mild steel, stainless steel, cast iron, brass, copper, nickel, and many other metals near to power source.

FAQs

Is AC or DC better for welding?

Both AC welding and DC welding have their own advantages and disadvantages. DC can be considered a better option because it allows aluminum welding and other metals. However, DC welding is a bit expensive, and you would have to spend more money using this type of polarity.

Are AC rods compatible with DC welder?

AC rods cannot be used for DC welders because each welding process requires a different filler metal. However, you can do so using an AC/DC welder. But make sure to select the correct polarity.

Summing Up

Being a part of the welding business, you need to know and understand the difference between AC and DC welding. AC and DC are both types of polarities. Both types have their own benefits and drawbacks.

DC output can weld many metal types except aluminum. But, experienced welders would like to have both AC/DC options, as some applications require AC output too.

Some top-quality TIG or multiprocess welders offers both AC/DC modes, and you can also choose between TIG and MIG.

DC polarities could pose some challenges in the beginning. But, as time passes, you will understand the difference between DCEN and DCEP.

The choice of the current type comes down to the type of metal that needs to be processed and the amount of money you are willing to invest. You can also look at the best AC/DC TIG welders in the market.

About Dave Walker

Dave Walker, a professional welder who has been welding from an early age. Now aims to help others by making them learning skills and finding them new opportunities. He has written for many welding blogs and helped many pursue their welding goals by helping them in choosing the best welding tools of the time.