Angle grinder with flap wheel Reduces thick paint
buildup or heavy rust over large, flat areas. Best as
an initial prep step. Removes everything rapidly,
including the metal itself, so be careful!
Wire brush (manual) Removes petrified grease
from vehicle parts. Helps remove loose or powdered
oxidation alongside other, more effective methods.
Needle scalers These earsplitting devices have a
high-speed wheel of thin, hard rods that successively
slam forward a few millimeters with each rotation.
They’re only useful on large rust that comes off in
scale form, such as on ships and bridges.
Abrasive blasting Excellent for removing paint,
rust, or other hard imperfections from any surface,
though less effective against softer coatings like
rubberized paints or heavy grease.
» The downsides are that this method is messy
and the equipment is expensive. You can use a
5hp/50gal air compressor ($200 on eBay or
Craigslist) with a small blasting gun, but more
power and volume are better. A $100 benchtop
blasting cabinet will speed the process, keep you
clean, and save you from having to sweep up
abrasives from your driveway.
» Do not use actual sand, ever, for “sandblasting,”
due to the risk of silicosis. Safe abrasives include
glass beads ($20 for 25lbs), aluminum oxide
(more aggressive; $50 for 25lbs), and ground
walnut shells (gentler but slow; $25 for 25lbs).
While blasting, keep dust out of your lungs by
wearing a real respirator with replaceable filters,
not a disposable mask.
» Moisture in your compressed air will cause more
rust later. A good cheap hack is to coil a long
length of the hose through a trash can full of
cold water and install a water trap at the downstream end.
» Filter your abrasive medium thoroughly for reuse
with a good sieve, or a series of 2 with decreasing
mesh size. Paint, grease balls, or other impurities
recycling through your gun will quickly lead to poor
performance and require gun disassembly.
Soda blasting This newer variant on abrasive
blasting uses water-soluble baking soda. Soda is
amazing for paint removal and for fragile materials
like brass, copper, aluminum, and glass, but not so
good with rust. Its solubility lets you blast pieces
and clean them up easily in place, without having to
remove them from engines or other locations where
loose grit would cause problems.
Soda blasting requires specialized equipment,
but prices (without the compressor) have fallen
“Homebrew” acids Vinegar, lemon juice, or cola
can remove light surface rust.
» These won’t work on heavy rust or paint. Stronger
acids do the job better, with no sugary mess to
clean up later.
Paint remover Removes paint (duh) but not rust
or corrosion. The best choice for painted, unrusted
parts, since it won’t affect the underlying metal.
» Less effective on powder coats; for these, try
multiple thick applications.
Alkaline rust removal (aka dip tanks or caustic
dips) Not recommended. This process involves
sodium hydroxide (lye) and chelating agent solutions
that are heated to near-boiling temperatures. It
produces nasty toxic vapors and waste, and unless
you have the right mix of chemicals, temperature,
and experience, it’s not as effective as the electrolytic
method on the following page.
Phosphoric acid and naval jelly Works alone to
remove light surface rust or as a secondary stage
following mechanical treatments.
» Heavy rust requires high concentrations of acid
and long immersion, which still might not work
on rust that has bloomed or turned to scale. With
lighter rust, spray the acid and let it sit for 30
minutes, covered with cling wrap to prevent drying. For faster results, the object should be warm.
» Phosphoric acid is very effective as a secondary
prep after mechanical treatment. It gets into
miniscule cracks (especially on cast iron) and
cleans out the bits of oxidation that even abrasive
blasting can miss.
» Auto parts stores carry phosphoric acid and zinc
preps for car body painting (e.g., POR- 15 Metal-Ready), which seal the metal surface with zinc
phosphate. Naval jelly, which can’t be sprayed, is
strong phosphoric acid in a thick medium to keep
it in place.