Ac Vs Dc Welding│Guide To Choosing the Right One

When regular people talk about AC/DC, know that they are talking about the Australian rock band. But when technicians talk about AC/DC, it’s either about electrical devices or different welding machines.

If you are about to start welding and want to buy a machine, it’s obvious that you feel confused regarding ac vs dc welding machines. Even though it seems that all welding machines do the same thing, the way of welding, efficiency, and finishing are the ones that highly differ the way of current flows in the machines.

Let’s have a better understanding of the differences between these two welding machine types.

General Welding Terms

It would be a lot easier to understand the discussion below if you have a clear idea about some of the basic terms related to welding. Welding makes two metal parts to join or connect by melting them together. Likewise, every electrical current, there are positive and negative poles in a welding arc within the polarity.

If you are not familiar with welding arc polarity, allow me to explain it in brief.

Welds are highly influenced by polarity, addressing its strength. Electrode-positive, also known as reverse polarity, makes penetration much deeper compared to electrode-negative polarity. On the other hand, electrode-negative polarity makes deposition of the filler metal much faster.

I think the above information will be enough for you to understand the differences between AC and DC welding.

Ac Vs Dc Welding Machine:

DC Welding

DC or direct current allows the charge to travel in one direction. It maintains a constant polarity to make the charge return and go in the same direction over and over.

In other words, DC currents make the electrons flow to one steady direction constantly. Due to its constant polarity, it can be positive or negative.

Even though DC polarity is widely used in low voltage devices such as remote controls, battery-powered devices, or machines, DC is only used in most high-end welding machines.

Compared to AC, it provides a smoother welding output. Also, the arc it creates is relatively more stable. It’s more user-friendly and easy. As there is much less spatter, the welder doesn’t need to spend much time cleaning hassle.

You have both the option to use DC positive for deeper penetration into the metal or DC negative for fast deposition rates while welding thin metal.

Due to the faster process of electrode negative, it quickly melts-off the electrode. Whereas, compared to the positive electrode, there is relatively less heat produced by the straight current; thus, it’s ideal for thinner metals so that the weld doesn’t melt too much of the metal.

Applications Of DC Welding

DC welding is good for stick welding processes. Also, vertical and overhead welding requires a DC current. Since AC isn’t suitable for stainless steel and aluminum TIG welding, DC is the only option in this case. It does better welds on thinner metals.


  • Ideal for stainless steel TIG welding, vertical welding, single carbon brazing, etc.
  • Produces a much lower amount of spatter
  • Smoother and higher in product yield
  • Consistency and stability of the electrical arc are what make DC more reliable
  • Welds thinner metals, unlike anything
  • DC requires the least expensive machines to function


  • Doesn’t hold up well against arc blow
  • Requires an internal transformer to switch AC into DC
  • Although the machinery is cheap, the whole DC process is expensive
  • Since it doesn’t produce intensive heat, it doesn’t weld aluminum materials well

AC Welding

When it’s about AC, it’s a type of current that makes the electrons always switch their directions. Within a second, polarity is changed 120 times on AC.

The polarity spins DC negative to positive every time, which causes the output to have zero amperage for a split second. If you are to use an AC welding process, make sure electrodes are specifically for AC welding purposes. There is a special coating that ignites the arc.

Compared to DC, the arc has more flutter and fluctuation on AC polarity.

In welding, AC is actually considered as a secondary choice. But there are some cases where AC is preferable. When it’s the only available power source, you have no option but to use it. Most basic, entry-level, and low-cost machines offer AC power only.

DC isn’t good for arc blow problems. Switching to an AC power source helps to fix the issue. Metal’s magnetism causes the problem while welding.

Positive-negative polarity alternation makes the arc a lot steadier while welding magnetic metals. Sometimes, windy conditions and some external issues are responsible for arc blowing problems.

Applications Of AC Welding

Since AC welding produces higher temperature heat, TIG aluminum welding is ideal for it. When AC current switches to electrode positive, it comes very effective at removing the tenacious oxide from the aluminum surface.

AC welding is also suitable in shipbuilding, where a deeper penetration into the plate metals is required. Welding any metal having a magnetic field also requires AC to be able to weld properly.


  • Aluminum TIG, down-hand, fast-fill, heavy plate, etc. welding can be done effectively
  • Frequent change of direction in AC is ideal for magnetized metal welding
  • Higher temperatures can be produced
  • Allows deeper penetration in metal surfaces
  • Seam welding requires an AC current
  • Repairing magnetic fields and rusted metals fit AC welding the most


  • Welding quality isn’t that smooth as DC welding.
  • Produces more spatter.
  • Comparatively less reliable than DC welding as it’s a bit difficult to handle.

Safety Procedures For Using Welding Machines

No matter whether you use an AC or DC welding machine, there are some common safety measurements that you need to follow while working. Some risks associated with welding can cause short or long-term illnesses.

Welding fumes can cause asthma or breathing problems. Also, burn is the most common injury that welders have to deal with. Ensuring personal protective equipment can reduce risks.

  • Be sure to wear fire-resistant clothing before you attempt welding. Even if the welding takes only a few minutes, make no mistake by not wearing protective clothes.
  • Always wear safety glasses while welding. The spark can reach the eye and cause severe consequences.
  • There are shoes to protect the legs.
  • Your hands can also contact the sparks. So, make sure you wear gloves as well.
  • Also, be sure to use a welding helmet, hood, and leather clothes.
  • Don’t wear synthetic clothing as it can melt when exposed to high heat. Wool can be a better choice as the material is fire-resistant.

Final Words

Even though DC welding is widely accepted and has more advantages than AC, there are situations when you are left with no other option but going for AC current to be able to weld properly. Once you understand how polarity works, you will be able to choose the right electrode along with proper polarity for welding metals.

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