How to Fix Metal Pitting

An angle grinder can be used to smooth out pitting in your metal.

After removing some sheet metal from the garage after long-term storage, you notice tiny pore-like holes on the surface. This type of corrosion is known as pitting, and it occurs when oxidation degrades the metal. A poorly applied protective coating or exposure to salt, moisture or abrasive chemicals may initiate pitting. There are a number of corrosion products that can mask the problem. You can, however, fix and eliminate the pitting and restore smoothness to your metal surface.

Things You'll Need

• Scrub brush
• Dish soap
• Cloths
• Bench vise
• Ratcheting pulley (optional)
• Cinder blocks (optional)
• Angle grinder
• Sanding disc
• Safety goggles
• Dust mask
• Penetrating lubricant
• Metal polish
• Buffing wheel

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Instructions

1. Clean the metal surface thoroughly with a scrub brush and a mixture of dish soap and warm water. Dry the metal completely using a soft cloth.

2. Secure the metal between the clamps of a bench vise. If your metal object is too large to secure with a bench vise, stabilize it with a ratcheting pulley or weight it down with cinder blocks.

3. Attach a 320-grit sanding disc to your angle grinder. Depending on the type of grinder you're using, disc installation procedure may vary. Refer to your tool's instruction manual for more specific instruction.

4. Put on safety goggles and dust mask. Turn on the grinder and set it to its medium speed. Touch the rotating disc to the pitted surface of the metal and apply firm even pressure. Move the disc across the pitting using a slow, side-to-side motion.

5. Turn off the grinder. Saturate a cloth with penetrating lubricant and wipe the metal free of dust to check your progress. If pitting is still visible, continue sanding until it appears smooth and the pitting is gone.

6. Wipe the metal completely clean with your saturated cloth. Attach a buffing wheel to your angle grinder.

7. Apply a generous layer of metal polish to the surface. Turn on the angle grinder and set it to its medium speed. Move the buffing wheel over the metal surface, again using a smooth side-to-side motion. For a high-shine finish, increase the speed of the grinder.

8. Wipe the metal clean with a damp cloth once the desired polish has been achieved.

Tips & Warnings

• Avoid metal pitting by storing your items in an airtight-watertight storage space. Protect metal surfaces with commercial sealants and regular cleaning.

• Most minor pitting can be removed by sanding with coarse grit sandpaper and burnishing with coarse steel wool. Clean the surface with a penetrating oil and follow with metal polish if desired.

• Handle your angle grinder with caution. The disc rotates at very high speeds and can cause injury if mishandled.

• Do not allow children or pets near your work area.

References

• Corrosion Doctors: Pitting Corrosion
• Roberts Cycle: Cleaning Chrome