AC vs DC Welding: Which is the Best Fit for Your Needs?

AC vs DC welding is one of the comparisons we as welders often consider, just like good vs bad welding.

Moreover, these two currents have their respective roles in welding.

Most welders prefer DC welding output for daily work operations. But AC welding output must also be considered in some welding processes.

As a beginner, you might be confused by my statement above.

What is the difference between these two current types, and why do you need to learn?

So, in the following article, I will guide you to better understand the information about both!

Here's What You Will Learn

Understanding AC Welding and DC Welding

Understanding the concept of AC and DC in welding is one of the fundamental things that beginners, even professionals, must know.

If you don’t see the idea, various potential problems can lurk.

Why is that?

Suppose you are welding and must choose one type of current; then you want to use the choice that matches the material and purpose of your work, right?

If you know the concept, you can make decisions faster and wiser. If you still have a vague understanding, you will have less wisdom in making decisions.

You seem to be betting on luck and feeling alone. This attitude is far from that of a professional welder, and I don’t want you to be like that.

Therefore, I will explain it all from the beginning. I am starting with the definition.

1. What is AC Welding?

AC (Alternating Current) in welding will switch the direction of the current back and forth for a second. By American standards, the outlet has an AC power of about 110 to 120 V and a frequency of 60 Hz.

When welding with this current, the electrode holder, TIG, torch, and ground clamp will switch polarity about 50-60 times a second.

But there is no need to worry about the AC input and output frequency because we can modify the output frequency value to be higher on new welding machines. Some can even produce 500 Hz.

2. What is DC Welding?

DC (Direct Current) in welding will flow in one direction only on the machine.

I use an electrode holder, a TIG/MIG torch, or a ground clamp to keep the electricity flowing because the electrical circuit must be continuous.

The arc will jump between the logan and the electrode to complete the electrical circuit with a pre-installed ground clamp.

Due to the electrical resistance of the metal, the metal and electrode will heat up to the melting point.

But remember, the weld quality can be drastically reduced if you choose the wrong polarity.

So ensure the electrode and ground clamp are connected correctly to the welding machine (power source).

Then, the polarity will depend on the electrode selection and the metal you are welding each time you weld.

Differences between AC and DC Welding

If you are familiar with AC and DC, you must have realized the general difference between the two.

Where AC will change polarity, and there is an alternating current flowing.

DC will ensure that the polarity remains uniform with the current flowing in one direction only.

Well, some of the essential differences between the two based on process aspects include:

1. AC vs DC Stick Welding (SMAW)

The first stick welders or buzz boxes are AC output machines with polarity switching that make a bee-like sound.

If we use this type to weld, the job can still be completed. But when compared to DC output, the arc is not stable.

Therefore, many DC machines are used for stick welding.

2. AC vs. DC TIG Welding (GTAW)

We can use AC and DC output when we want to do TIG welding, depending on the material you are welding.

For AC output, it is usually for magnesium and aluminum materials. For DC output, the materials are carbon steel, mild steel, and stainless steel.

3. AC vs DC MIG Welding (GMAW)

For MIG welding, it is better to use DCEN (Direct Current Electrode Negative) as in stick welding. Then aluminum MIG welding DCEP (Direct Current Electrode Positive) is also needed.

But that does not mean AC output is not used in MIG welding because it is also widely used in the industrial field—for example, AC aluminum pulse welding and transfer welding.

4. AC vs DC Flux-Cored Welding (FCAW)

For core welding, the DCEN polarity requires self-shielded flux-cored.

So like most of the above comparisons, we are better off using the DC version for maximum weld results.

Pros and Cons of AC vs DC Welding

Each of these currents certainly has advantages and disadvantages, so it can be considered when choosing it.

Below, I have summarized some of the advantages and disadvantages of both.

1. AC Welding

Some AC welding advantages include the following:

Because of the DCEP phase, we can weld magnesium and aluminum using the TIG welding process.
When you use long cables, AC will not experience pressure drop, so it can be used when TIG welding and stick welding, which sometimes require long wires because they are far from the power source.
AC stick welding machines are realistically cheaper,
The arc is more stable when welding metals susceptible to magnetic fields. The way it works is by preventing arc blow and arc deflection.

While the disadvantages of this welding are:

When welding stainless steel and mild steel, there will be a lot of spatters or a lack of arc stability.
The welding quality is below the DC output.
The price of AC TIG last is higher than using a DC TIG machine.

2. DC Welding

Now for DC welding advantages that we will feel is:

The arc is much more stable when using DC output than AC when doing stick welding.
The shape of the weld is similar, so it is much easier to operate when we change the machine.
Because it is easier to control, the SMAW arc can help you to direct the liquid filler metal well.
Less spatter is produced than AC output
When stick welding, DCEP can make better penetration.
When stick welding, DCEN can provide a faster metal deposition rate. But it should be used on thin sheet metal due to its reduced penetration.

While DC output disadvantages are:

Due to the deflection and arc stroke, you will find it difficult to weld metals with a magnetic field.
Metals like aluminum cannot be welded with DC TIG and SMAW.
The equipment is more expensive.

Considering the various aspects of AC vs DC welding above, I recommend you choose DC welding. But for some cases, please consider using AC welding.

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