Welding with 7018: Should You Use AC or DC Current? When to Use 7018AC

Introduction

Welding with 7018 electrodes is a staple in shielded metal arc welding (SMAW), also known as stick welding. The answer to “AC or DC?” depends on the exact electrode and welding procedure, not just the 7018 name. Some standard E7018 products support both AC and direct current electrode positive (DCEP). A 7018AC product may help on an AC machine with low open-circuit voltage, but check its manufacturer’s instructions before buying or changing settings.

Types / Variants / Models

• Standard E7018 example: Lincoln Excalibur 7018 MR lists DC+ as the preferred polarity and also lists AC.
• 7018AC example: Lincoln 7018 AC lists AC as preferred and also permits DC+. Its low-open-circuit-voltage capability and restrike characteristics are product features; “7018AC” does not mean every such electrode is AC-only.

These examples come from Lincoln’s consumables catalog, pages A-1 and A-8. Do not transfer one product’s polarity or amperage recommendations to another brand or diameter.

Key Features or Specifications

• Coating: E7018 is a low-hydrogen, iron-powder electrode. Moisture control remains important; the designation does not promise crack-free welds.
• Current type: DCEP means electrode positive, also written DC+. It is different from DCEN or DC−. Follow the exact product’s permitted polarity and your machine manual.
• Sizes and settings: Available diameters and recommended current ranges vary by product. Match the electrode to the joint, position and equipment rather than using thickness alone.
• Classification and approvals: Check the full AWS classification and any required product approvals. A classification alone does not establish that a completed structural weld is suitable or code-compliant.

See Hobart’s E7018 guidance and Miller’s electrode-selection guidance for the factors that govern selection.

Usage & Compatibility

Welding Process

7018 electrodes are used for SMAW (stick welding). Selecting the process or electrode does not by itself ensure weld strength.

Machine Compatibility

• DC machines: Confirm the required output polarity. For a product that prefers DCEP, use that recommendation unless the applicable welding procedure specifies another permitted option. Do not assume DC always gives deeper penetration than AC.
• AC machines: Confirm that the electrode supports AC and is compatible with the power source. Low open-circuit voltage (OCV) concerns the welder’s output before the arc is established. It is not the same as fluctuating input power, and a 7018AC label is not a remedy for an inadequate power supply.

Miller’s welding dictionary explains DCEP, DCEN, OCV and primary input power.

Common Applications

E7018 products are used in structural fabrication and other work such as shipbuilding. Pipeline, load-bearing and other critical joints require the electrode, base metal, service conditions and applicable welding procedure specification (WPS) to match the job requirements. Neither a “7018” label nor the choice of AC versus DC guarantees joint durability, fatigue resistance or acceptance by inspection.

Tips & Best Practices

• Before setup: Check the exact product and diameter, permitted polarity, manufacturer’s current range, welding position and machine instructions. For code work, follow the applicable WPS and qualification requirements.
• Storage: Keep sealed packages closed until needed. After opening, follow the product’s heated-holding instructions and permitted atmospheric-exposure limits. Use an electrode-storage oven when specified. Requirements vary by product and welding code; “keep dry” alone is not an adequate low-hydrogen storage plan.
• Reconditioning: Holding and redrying are different operations. Follow the manufacturer’s exact time and temperature instructions, and any code restrictions. Do not improvise a generic rebaking recipe. If the storage history is uncertain, seek manufacturer guidance before critical work.
• Arc troubleshooting: Review the machine instructions and work-return connection with a qualified welding instructor or supervisor. The workpiece lead is part of the welding circuit, not the machine’s protective earth connection. Do not alter protective grounding to troubleshoot the arc. Changing to a 7018AC product while the machine remains on DC does not change the output to AC.

Storage guidance: Lincoln’s storing and redrying guide and Hobart’s filler-metal handling guidance. No universal oven temperature or exposure period is prescribed here.

Conclusion

Choose AC or DC from the exact electrode instructions, machine capabilities and job procedure. Consider a low-OCV 7018AC product when that capability is needed and the product is approved for the work. Correct polarity and controlled storage are important checks, but they do not replace a suitable procedure, sound technique or required inspection.