After my original post requesting information about what was in the
commercial rust strippers, I did a little research. The only chemical
research I usually do involves different brands of beer. Consequently, I'll
give you the raw info from the article.
From: ASME Metals Handbook Vol 2 8th ed. "Heat Treating, Cleaning, and
Finishing"
Article titled: "Acid Cleaning of Iron and Steel" by The ASM Committee on
Acid Cleaning
"...The phosphoric acid-ethylene glycol monobutyl ether [try dropping that
into a party conversation] mixtures are widely used for removing grease, oil,
drawing compounds, and light rust from iron and steel. In various
concentrations, as shown [below] they are adaptable to immersion, spray or
wiping methods and leave a light phosphate coating.
..to clean cast iron and stainless steel... a typical chromic acid formula
for cleaning stainless steel is 8 oz CrO3, 8 oz H2SO4, and 8 oz HF per gallon
of water, for use at room temperature in an immersion system.
..to clean rust without attacking the metal, mix 10 oz of citric acid per
gallon of water, add ammonia until the solution is alkaline (pH 7.5 to 8.0),
heat to 190 to 200 F, and immerse the parts...hydrogen embrittlement will not
occur.
..Other typical formulations used for wipe cleaning are:
a) 6 to 8% sulfuric acid (by volume) in water,
b) 70% phosphoric acid, 5% wetting agent and 25% water, and
c) a paste made of 85 to 95% ammonium dihydrogen phosphate and the remainder
wetting agent, used on a wet cloth or sponge
..Table 1 Acid Cleaner Formulations
Composition, % by weight
Item Immersion Wipe
Phosphoric acid 70 15 to 25
nonionic wetting agent* 5 7 to 20
other additives inhibitors inhibitors
(up to 1%) (up to 1%)
Water balance balance
Concentration, oz per gallon 16 ----
Temperature, F 160F Room
* Ethylene glycol monobutyl ether is commonly used [as a wetting agent]
[the inhibitors are used to minimize attack on metal-little detail given]
..an operator suitably protected...wipes the soiled work pieces with an acid-
impregnated cloth or sponge. After the cleaner is allowed to react (2 or 3
minutes is usually sufficient) the work is rinsed with water."
I'm still curious as to where the zinc part of the "zinc phosphate" in the
commercial (Eastwood) cleaner comes from. 'Anybody know?
Sean "ethylene glycol monobutyl ether" Johnson
'79 MGB '75 Spitfire
P.S. I got a posting suggesting trisodium phosphate. Drano is not TSP any
more; the lable says "Calcium Hypoclorite" and "no phosphates"
P.P.S. The book also has formulations for non-ferrous metals- see next
exciting installment!
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