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Paul, Another off the shelf product containing oxalic acid is Zuds. It
comes in a liquid slurry or a powder much like a cleanser product. It also has abrasives
like cleansers so it may scratch some surfaces. I use around the house occasionally for
removing light rust stains from wood, some fabrics, concrete, and countertops.
I am a little “rusty” on my chemistry,
but I believe oxalic works as a reducing
agent that a takes the ferric iron (rust) to soluble ferrous state. It may also
have chelating properties like citrates, but I am a not sure of that. Like most everything else in substitution assessments,
it has some risks. I found this
definition via Google: A dicarboxylic acid, chemically COOH—COOH. Poisonous in large
amounts; present especially in spinach, chocolate, rhubarb, and nuts. The
toxicity of rhubarb leaves is due to their high content of oxalic acid. High concentrations of oxalates in the urine
can form kidney stones; while most of these oxalates are of endogenous
metabolic origin, patients with hyperoxaluria are advised to avoid dietary
sources of oxalates. So if you use oxalic
acid products around Thanksgiving, you may want to go light on the rhubarb pie –
at least a second helping. John
Sparks From: owner-p2tech@great-lakes.net
[mailto:owner-p2tech@great-lakes.net] On Behalf Of Callahan, Mike Paul, The
most common way to remove rust stains is with an acid. Hydrofluoric acid
is most effective but very dangerous to handle. Commercial rust removers most
often contain oxalic acid. Bar Keepers Friend is a scouring powder with
oxalic acid. Being an organic acid, oxalic acid is biodegradable and acceptable
for sewer discharge. The abrasive solids might be an issue, but only if you
were trying to use them on an industrial scale. Small use on an occassional
rust stain should not be an issue. I don't know if any commercial
products use citric acid, but it too should be capable of removing light rust
stains. Once the stain is removed, you want to flush the surface with lots of
water (to remove the acid) and if metal, apply a protective oil-based coating.
Acid cleaned metal will quickly rust again if you don't take measures to
protect it from air and moisture. Hope this helps. Mike
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