What is reverse polarity in welding? Welding is a fascinating process. Lots of folks take up welding as a tool to complete a challenging DIY project. Knowing how to weld creates plenty of opportunities and broadens your horizons.
We strongly believe that understanding the nature of the processes you are engaging in raises your skill level exponentially. Reverse polarity is a critical basic term in the welding process.
Let us give you a quick run through the reverse polarity and adjacent concepts (e.g., straight polarity) to obtain a general awareness of the physical proceedings and understand the distinction between straight and reverse polarity.
It’s worth noting that the knowledge we are offering is not purely theoretical. As it often happens, it has a critical impact on the welding process you plan to engage in.
Contents
Reverse polarity: definition
Electron flow from the positive pole to the negative pole is the definition of the reverse polarity. The workpiece constitutes the negative pole, and the electrode — is the positive pole.
This is a short version of the concept.
If our definition is not clear enough because you are not familiar with basic processes in an electric circuit, we’ll provide a more detailed explanation.
Understanding reverse polarity: critical concepts
To get the hang of polarity in welding and, to be more precise, reverse polarity, we will need a couple of definitions.
- Different currents. There are two types of currents: direct current, usually referred to as DC, and alternating current, or AC. DC flows on the same course without alternating it. Unlike AC, which changes the flow direction from time to time. It’s important for understanding the polarity in welding.
- Polarity. An electric circuit required for the welding machine to function always has a certain pole. That is polarity. The dual alternatives are a positive pole and a negative pole. In the first case, we are dealing with reverse polarity, and in the second — with straight polarity.Depending on the type of current in the circuit (DC or AC), the polarity is referred to as constant polarity, although you can come across the term DC reverse polarity, and alternating current polarity.
The distinction between reverse polarity and straight polarity
As we already know, DC reverse polarity in welding implies that the charge flows from the workpiece to the welding electrode, thus creating higher temperatures if compared to the DC straight polarity.
You can come across another expression for reverse polarity in welding, so don’t get surprised: Direct Current Electrode Positive.
Direct current straight polarity (another conventional term is Direct Current Electrode Negative) implies a negative electrode and a positive workpiece.
The electrode is estimated to create around 70% of the welding arc heat on the electrode tip, thus causing a swift metal deposition.
Reverse polarity welding has its advantages, such as speed and high-quality welding when processing fine items. Besides, inclusion defects are generally avoided with direct current reverse polarity thanks to the welding arc cleaning feature.
As for the metals chosen for direct current reverse polarity welding, the overall recommendation is to opt for the ones with low melting temperatures, like copper or lithium.
Among the disadvantages of welding reverse polarity is its less efficiency with thicker pieces of metals, which have higher melting temperatures. Additionally, electrodes are disposed of faster.
Straight polarity welding has its advantages, too. Like a smoother, more even welding result caused by the heat distribution, which is more constant compared to reverse polarity welding.
Speaking about polarity, we can’t avoid mentioning alternating current polarity. As we have already mentioned, apart from DC welding practices, there are also methods using AC welding techniques.
With the power source providing AC, you will observe both welding reverse polarity and its counterpart — straight polarity, both for the duration of half of the cycle. For one half, the metal piece is coupled with the positive terminal, but then the roles will change, and the electrode will be positive, and the plates will be connected to the negative terminal.
AC polarity welding possesses the features of both DC polarities, hence its diverse application.
Choosing welding polarity: utilitarian approach
Using the wrong polarity creates additional challenges for the process, which is not easy in the first place. To choose appropriately, look at the problem from different perspectives.
Start with estimating if the metal is thin or thick. For thicker pieces, opt for direct current straight polarity.
Melting temperatures are one more factor to keep in mind. Reverse polarity welding is preferable for such metals as copper and magnesium, whereas such metals as stainless steel will require AC polarity for optimum efficiency.
Having the best of two worlds, it provides the perks of DC Electrode Positive (a.k.a. reverse polarity welding) as well as of straight polarity, as the current is changing direction during this process.
Also, with reverse polarity, the arcs have a high degree of penetration.
Hence, its wide use in small spaces when it’s too complex to reach the rear part of the piece.
High speed and shorter arcs of reverse polarity welding are other factors that are considered while making the choice of the polarity to be used.
And one last note: check the availability of the power source you need, whether it’s a power source for AC or DC.
Conclusion
The question: what is reverse polarity in welding is absolutely legitimate and important for everyone keen on welding and may be thinking about purchasing a welding machine.
Knowledge about polarity, DC welding, AC welding, and more is significant if you are taking this craft seriously and are planning to make substantial progress.
Knowledge is not theoretical: it makes a practical impact on the final products of the welding process.
FAQ
Why would you reverse polarity on a welder?
The most common reason to use reverse polarity is the intention to permeate the material deeper. Besides, this type of polarity is preferable for metals with low melting temperatures.
What is the difference between straight and reverse polarity?
Reverse polarity implies the electrode’s connection to the positive terminal and the plates — to the negative. Straight polarity is the opposite: negatively connected electrode and the plates that are connected to the positive terminal.
What is reverse polarity?
Reverse polarity takes place when the charge moves from the positive electrode to the negative workpiece.
Do you need straight or reverse polarity for MIG welding?
For MIG welding, reverse polarity is required.