How to Repair Pitted Aluminum

By Susan Kerr

Aluminum is lightweight and widely used in the automotive industry for body panels. Its lightness also makes it ideal for boats and canoes. Unfortunately, it reacts with salt water and iron through a chemical process called electrolysis. The result is a chalky white oxidation that weakens the metal. Complete removal of surface pitting and oxidation is the only way to stop its further deterioration. Priming the bare metal prepares the surface for a protective coat of paint. Primers and paints vary in their components and formulations, so following the manufacturers' directions exactly is the key to getting good results.

List of Items Needed

  • Handheld rotary tool with grinding stone, abrasive wheel and/or abrasive point accessories
  • Handheld sandblasting gun
  • Acrylic sandblasting material
  • Stainless steel brush
  • Masking material
  • Primer
  • Basecoat and clear coat (optional)
  • Safety goggles
  • Protective mask
  1. Grind the corrosion off with a handheld rotary tool, fitted with a grinding stone, abrasive wheel or abrasive point accessory. Aluminum is a soft metal, so the accessory might become clogged and require cleaning. An alternative to grinding is sandblasting, using a portable sandblasting gun and acrylic blasting material.

  2. Isolate tools used in repairing aluminum surfaces from tools used on other metals. Cross contamination between metals can cause electrolysis, a molecular reaction that accelerates corrosion. Use only a stainless-steel brush on an aluminum surface during repair.

  3. Protect any adjacent surfaces with masking material before applying primers or paint. Apply a body primer if the manufacturer doesn't specify a particular type for bare metal. Read the directions carefully because some epoxy primers require the application of heat for proper curing. Use several thin coats of primer and allow each one to dry before you apply another. Sand the primed area with 400- to 600-grit sandpaper and feather the edges.

  4. Apply automotive basecoats according to the manufacturer's instructions if you're working on a car. Allow the basecoat to flash, or cure, for the time specified in the instructions. Sand it again if you need a very smooth surface, then apply a second coat like the first. Sand again. Apply one or two coats of clear coat following the manufacturer's guidelines.

Tips and Warnings

  • Sandblasting is the preferred method for removing aluminum corrosion, and used in the automotive industry. However, if you own a handheld rotary tool and not a sandblaster, the rotary tool is a good substitute, eliminating the need to go out and rent a heavy power tool.
  • Sand away the corroded aluminum and don't rely on claims about chemical treatment options. Their effectiveness has been challenged.
  • Complete removal of oxidized metal is necessary to prevent further deterioration.
  • Do not grind corroded aluminum surfaces unless you really have to.
  • Don safety goggles whenever you grind metal.
  • Wear a protective mask while removing old paint and oxidized metal and when applying epoxy primers. Older paint may contain lead. Metal oxides may lead to health problems if they are inhaled or ingested. Primers may contain petroleum distillates that are harmful when breathed.

© Demand Media 2011