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Tag: TIG prep

  • How to Prep Metal for Welding (Step-by-Step Guide)

    How to Prep Metal for Welding (Step-by-Step Guide)

    Proper metal prep is the difference between a clean, strong weld and fighting porosity, inclusions, and arc instability. This guide breaks down exactly how to clean, grind, degrease, and fit-up steel, stainless, and aluminum so you can weld with fewer defects and less rework.

    Key Takeaways

    • Clean metal = fewer porosity and arc-start issues. Remove mill scale, rust, paint, oil, and coatings.
    • Use the right abrasives: flap discs for beveling, hard wheels for aggressive cleaning, and stainless-only tools for stainless.
    • Fit-up accuracy determines distortion control and penetration.
    • Always check safety: ANSI Z87.1 eye protection, proper ventilation, and PPE.
    • Improper prep is one of the Top 3 causes of weld failure per AWS D1.1 commentary.

    Where to Buy (Tools for Metal Prep)

    Arc Weld Store:

    40-grit flap discs — Heavy removal

    Weldcote 10668 Flap Discs C-Prime Ceramic 4.5" 40 Grit XL 7/8" Arbor 10 Pack T27 13300 RPM

    Weldcote 10668 Flap Discs C-Prime Ceramic 4.5" 40 Grit XL 7/8" Arbor 10 Pack T27 13300 RPM

    $86.93

    In Stock

    View Product
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    Weldcote 10668 Flap Discs C-Prime Ceramic 4.5" 40 Grit XL 7/8" Arbor 10 Pack T27 13300 RPM

    Weldcote 10668 Flap Discs C-Prime Ceramic 4.5" 40 Grit XL 7/8" Arbor 10 Pack T27 13300 RPM

    $86.93

    In Stock

    View Product

    80-grit flap discs — Finishing before weld

    Weldcote 10670 XL Flap Discs - C-Prime Ceramic 4.5" 80 Grit 7/8" Arbor - 10 Pack

    Weldcote 10670 XL Flap Discs – C-Prime Ceramic 4.5" 80 Grit 7/8" Arbor – 10 Pack

    $70.03

    In Stock

    View Product
    “>
    Weldcote 10670 XL Flap Discs - C-Prime Ceramic 4.5" 80 Grit 7/8" Arbor - 10 Pack

    Weldcote 10670 XL Flap Discs – C-Prime Ceramic 4.5" 80 Grit 7/8" Arbor – 10 Pack

    $70.03

    In Stock

    View Product

    Amazon (options):

    Affiliate Disclosure: As an Amazon Associate, we earn from qualifying purchases.

    How to Prep Metal for Welding

    1. Identify the Material

    Different materials need different prep steps.

    Carbon Steel

    • Remove mill scale (blue/black surface).
    • Grind out rust, paint, coatings, and galvanizing.
    • Bevel edges for thicker plate (¼ in / 6 mm and up).

    Stainless Steel

    • Use stainless-dedicated wheels only (never shared with carbon steel).
    • Remove heat tint and oxide layers.
    • Clean surface oils with acetone before welding.

    Aluminum

    • Remove oxide layer mechanically (stainless brush).
    • Degrease with acetone or alcohol.
    • Wire-brush immediately before welding — oxide reforms in minutes.

    2. Remove Coatings, Rust, and Mill Scale

    Tools that work:

    • Flap disc (40–60 grit)
    • Hard grinding wheel
    • Wire wheel (for light rust)
    • Needle scaler (heavy rust or slag)

    Remove down to bright, shiny metal. For carbon steel, AWS D1.1 recommends removing contaminants within 1 inch (25 mm) of the weld area.

    3. Degrease and Clean

    Oil, cutting fluid, and shop grime cause porosity.

    • Use acetone or denatured alcohol.
    • Avoid oily solvents like WD-40.
    • Wipe until the rag stays clean.

    Tip: Do solvent cleaning before grinding (to avoid driving oil into the pores) and again after to remove grinding dust.

    4. Fix Edges, Bevels, and Gaps

    Fit-up sets the stage for the entire weld.

    • Bevel: 30–37.5° for structural steel (AWS standard).
    • Root opening: 1/16–1/8 in. depending on joint.
    • Remove burrs for full penetration.
    • Tack weld at opposite ends to reduce movement.

    5. Clean Again Before Welding

    Right before striking an arc:

    • Blow off dust
    • Wipe with acetone (stainless + aluminum)
    • Ensure the joint is dry — moisture = hydrogen

    Safety Notes

    • Wear ANSI Z87.1 eye protection and face shield when grinding.
    • Use gloves, FR clothing, and hearing protection.
    • Avoid grinding galvanized steel — zinc fumes require strong ventilation or removal + respirator (P100).
    • Keep flammables away — grinding sparks can exceed 1,800°F.
    • Ensure proper fume extraction for stainless to reduce hex-chrome exposure.

    FAQ

    Do I have to remove all mill scale?

    For critical welds (per AWS D1.1), yes. For hobby MIG on light steel, partial removal can work, but expect spatter and inconsistent penetration.

    Can I weld through paint?

    Not recommended. Most paints give off toxic fumes and produce porosity.

    How clean does aluminum need to be?

    Extremely clean. Oxide melts at ~3,700°F; aluminum melts at ~1,200°F. That’s why aluminum requires brushing + solvent cleaning.

    Why do my welds have porosity even after grinding?

    Usually oil contamination or moisture. Try degreasing and pre-heating to ~150–200°F.

    Sources Checked

    • AWS D1.1 Structural Welding Code – Steel
    • Miller, Lincoln, ESAB abrasive and prep guides
    • ANSI Z87.1 PPE requirements
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