What Is The Difference Between AC And Dc Welding?

by James Anderson | Last Updated on February 17, 2023

For someone familiar with how welding works knows that different current types are used in the process. You might have heard the terms “AC” and “DC,” right? Don’t get confused with the rock band AC/DC, though. AC and DC are different types of current that are used in the welding process.

Arc welding is something you should make yourself familiar with. It is a type of welding process that uses an electric arc to create heat. To create an electric arc, alternating current or direct current is used. The electric arc creates an intense heat of about 6500 F. The polarity of the arc entirely depends on the type of current source you use. One wrong decision while choosing the suitable current will lead to a total disaster. This is why you need to be sure about the type of welding current you find appropriate.

To get into welding, it is also essential to know about polarity in welding. Polarity matters a lot in welding because it affects the stability and quality of the weld. Most of the time, you will notice that the electrodes are labeled as ‘AC’ or ‘DC’; this describes the polarity of the machine’s current. Here AC and DC mean alternating and direct current. In alternating current, the flow of current is not unidirectional. While in DC, the flow of current is unidirectional.

Which current is better? AC or DC?

Personally, I believe that there is no ‘better’ current between the two. Both of the power sources are used for different purposes. I might not sound convincing now but you will understand what I am talking about at the end of the article.

When I was starting, I faced something horrible while welding for the first time. I used the wrong welding current, which resulted in lots of splatters, insufficient penetration, and almost no control of the welding arc. This happened because of my lack of knowledge on polarity and welding current. My main concern was, which welding current is right then?

So, here I am to finally end the debate on the difference between AC and DC welding. You can choose the suitable welding current after knowing the differences. Here you go!

AC Welding

An alternating current source does not have a constant polarity. The current changes its direction, so there is variable polarity. The polarity flows in one direction for half of its time and in reverse for the other half.

AC welding is rarely used in comparison to DC welding. But, it has a lot of benefits and can be used for numerous purposes. The type of current you choose mostly depends on the type of material you are working with. For instance, AC Welding is more suitable for heavy plate welds, fast fills, and magnetized metals. Note that DC sources can not be used while welding magnetized metals. Welding machines can use AC sources instead because the constant change in the current’s direction negates the magnetized metal’s effect on the electric arc. Sounds great, right?

Apart from these, AC welding is also a great choice in terms of maintaining a higher temperature. The higher current level creates a deeper penetration. It is also suitable for repairing machinery that has magnetic fields fixing problems with arc blow.

Advantages

• The change in the direction of current creates a negative and positive polarity that provides a more stable arc for welding magnetic metals.
• Quickly fixes problems with arc blow.
• Effectively welds aluminum
• AC welding machines are cheaper
• Can weld materials that have magnetic properties
• AC welding machines are smaller in size and easy to use
• Maintaining an AC welding machine is easier
• It can be used at a considerable distance because the voltage drop is more minor.

Disadvantages

• Creates more splatter
• The arc is hard to handle
• The quality of the weld is less smooth than welding with a DC source
• Specially coated electrodes can only be used

DC Welding

In the case of a DC power source, the current flows in a single direction. So, it has a constant polarity. The produced current can be positive or negative.

Just like AC welding has its benefits, DC welding also has its perks. It can be used for vertical welding, single carbon brazing, and stainless steel welding. DC welding also has a higher deposition rate that allows the better build-up of larger deposits.

Best of all, DC welding has a higher product yield. In comparison to AC welding, it produces less spatter, and the weld is also smoother. DC power sources are also easier to work with because the electrical arc remains stable. They are the most suitable for welding thinner metals.

Advantages

• The electric arc is stable.
• Smoother welding output
• Provides less spatter
• Has a faster deposition rate
• Coated and bare electrodes can be used
• Perfect for thin metals

Disadvantages

• The machines are heavy and costly.
• Maintenance cost is also very high
• It can only be used at a short distance
• Arc blow cannot be controlled, and it is severe.
• Cannot weld metals that have magnetic properties

Frequently Asked Questions (FAQ)

Q: Do you need ac or dc to weld aluminum?

For welding aluminium, AC current is required. It is used because the initial half cycle of the current gives a cleaning action. Whereas, the other half is solely for penetration. On the other hand, DC is used to weld stainless steel.

Q: Can You Use AC Rods in a DC Welder and Vice Versa?

AC and DC rods cannot be interchanged in DC welding. Only AC rods can be used in AC welder and vice versa. Because the filler metal that is used for welding is different. Apart from this, the conditions for an AC welder and DC welder differ a lot too. So using the wrong rod is a big NO.

Q: When to use AC Vs DC welding?

There is no ‘right time’ or ‘condition’ for using AC or DC welding. It all depends on what you want from the weld. If you want a smoother output, less spatter, and a more stable arc, then you should definitely go for DC welding. On the other hand, AC welding also has its perks. If you are looking for more minor problems with the arc blow, effective aluminum welding, and cheaper equipment, then AC welding is the right choice for you. So, the type of current entirely depends on the outcome you want.

Bottom Line

The debate between which current is better, AC or DC, is finally coming to an end. Personally, I think that if you want good results, focus on polarity. Since the type of current being used affects the polarity at the electrode, you also need to focus on the electrode. There are electrodes available for both DC and AC welding.

To sum it all up, I think there is no “better” type of current in welding. Both AC and DC welding have their benefits and drawbacks. It all depends on the type of metal you are welding or how much you can invest in welding. For instance, if I weld a magnetic metal through DC welding, the results would be pretty bad. Hence, it’s entirely up to you to find the most suitable current source.