Definition
In AC arc welding of aluminum, rectification is the condition in which the alternating current flow becomes unbalanced because the oxide layer on the aluminum surface acts like a one-way valve, allowing current to pass more easily in one direction than the other. The result is that the AC waveform partially behaves like direct current, which disrupts the cleaning action and the heat balance needed for a sound weld.
Plain English
When welding aluminum with alternating current, the tough oxide skin on the metal lets electricity flow more easily one way than the other. This throws the current out of balance and turns part of the back-and-forth flow into a one-way flow, which causes welding problems.
Context Anchor
Seen in aircraft maintenance welding discussions, especially when an alternating-current arc weld is unstable or not behaving normally.
Derivation
From Latin rectus, meaning 'straight' or 'right.' To 'rectify' a current is to straighten alternating current into direct current. In welding, the oxide layer unintentionally does some of this straightening, which is why the condition carries the name.
Why Pilots Care
Aircraft technicians welding aluminum structures must understand rectification because it degrades weld quality. High-frequency current is added to AC welders specifically to overcome it, and recognizing the symptom helps the technician troubleshoot equipment and weld appearance.
Analogy
Think of a swinging door that is supposed to move equally both ways, but it starts opening more easily in one direction. Rectification is similar: the welding current is supposed to alternate both ways, but the arc favors one direction.
Intuition Check
Rectification does not mean “fixing a mistake” here. In this welding context, it means an alternating electrical arc is becoming uneven and partly one-directional.
Example Sentence 1
The technician switched on the high-frequency stabilizer to prevent rectification while AC welding the aluminum fitting.
Example Sentence 2
Adjusting the electrode balance restored proper AC flow and eliminated the rectification condition.