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Home News Why AC Current Is Essential for Aluminum Welding？
Publish Time: 2025-11-13
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Aluminum is everywhere—from smartphones and laptops to aerospace components—valued for its light weight, corrosion resistance, and aesthetic appeal. However, welding aluminum presents unique challenges that often require alternating current (AC) rather than direct current (DC). Here’s why.


The Challenge: Aluminum’s “Invisible Armor”

Aluminum rapidly reacts with oxygen in the air, forming a thin, dense layer of aluminum oxide (Al₂O₃). This oxide layer acts as a barrier during welding. 
Key Properties:

  • Melting point of pure aluminum: 660°C (1220°F)

  • Melting point of aluminum oxide: 2050°C (3722°F)

This mismatch means the oxide layer remains solid while the underlying aluminum melts, preventing proper fusion and weld formation using conventional DC methods.


How AC Solves the Problem: Cathodic Cleaning

Alternating current enables a two-step process that breaks down the oxide layer and welds the metal effectively 
1. Electrode Positive (EP) Cycle: “Cleaning” Phase

  • Positively charged argon ions bombard the workpiece surface.

  • This “cathodic cleaning” or “oxide breaking” action shatters and disperses the aluminum oxide.

  • Results in a clean, shiny surface ready for welding.

2. Electrode Negative (EN) Cycle: “Welding” Phase

  • Heat concentrates on the workpiece, melting the aluminum.

  • Forms a stable weld pool with deep penetration.

This continuous alternation between cleaning and welding makes AC ideal for aluminum.


Why DC Falls Short

DC Electrode Positive (DCEP)

  • Provides strong oxide cleaning but causes extreme tungsten electrode overheating.

  • Leads to rapid electrode degradation and unstable arcs.

DC Electrode Negative (DCEN)

  • Offers good penetration but cannot remove oxides.

  • Results in contaminated, poor-quality welds.

Thus, DC is rarely practical for aluminum welding outside particular applications.


Modern Advances: Square Wave AC & Inverter Technology

Newer welding machines use advanced square wave AC that improves upon traditional sine wave AC:

  • Adjustable cleaning-to-welding ratio.

  • Improved arc stability and control.

  • Enhanced energy efficiency and weld quality.

Operators can fine-tune settings based on material thickness, surface condition, and desired weld characteristics.


Conclusion

AC TIG welding remains the gold standard for aluminum due to its unique ability to overcome the oxide layer through cathodic cleaning. While technology continues to evolve, AC’s role in aluminum welding remains essential—enabling everything from everyday consumer products to cutting-edge aerospace designs.


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