AAC Advanced Techniques & Applications
Advanced AAC applications, polarity for mild steel, air jet positioning, groove width control, and electrode stickout.
- Identify the most common application of the AAC process
- State the recommended polarity for AAC on mild steel
- Describe correct air jet positioning on the AAC torch
- Explain the factors that control groove width and depth
- State the optimum electrode stickout and recommended air pressure
Lesson 1
AAC Applications & Polarity Selection
Common Applications of AAC
The most common application of the AAC process is removing weld faults. When a weld fails inspection due to cracks, porosity, lack of fusion, or other defects, AAC gouging is the preferred method for removing the defective material so the joint can be re-welded. The process is also widely used for back gouging - removing the root of a weld from the back side to ensure complete joint penetration on double-sided welds.
Primary AAC Applications
Removing weld faults - cracks, porosity, lack of fusion
Back gouging - preparing root for second-side welding
Preparing U-grooves - in heavy plate before welding
Removing old welds - during repair and maintenance
NOT Typical AAC Applications
Precision cutting - PAC or OFC preferred for through-cuts
Thin material - too much heat input for thin sheets
Reactive metals - titanium requires inert atmosphere
Recommended Polarity
The recommended polarity for air carbon arc gouging of mild steel is DCEP (Direct Current Electrode Positive). With DCEP, the electrode is connected to the positive terminal of the power source. This polarity provides the most stable arc and the best balance of electrode consumption rate and metal removal efficiency for carbon steel applications.
DCEP for AAC on Mild Steel
Remember: DCEP (electrode positive) is the standard polarity for AAC on mild steel. This is a frequently tested exam fact. DCEN and AC are used only for special applications.
AAC vs OFC - Main Advantage
The main advantage of using the AAC process over the OFC process is that AAC can cut ferrous and nonferrous metals quickly. OFC is limited to ferrous metals because it relies on an oxidation reaction. AAC uses electric arc heat, making it effective on stainless steel, cast iron, copper, nickel alloys, aluminum, and all other conductive materials.
The most common AAC application is removing weld faults. Use DCEP polarity for mild steel. AAC's main advantage over OFC is cutting both ferrous and nonferrous metals.