On 12/1/15 10:37 AM, Electric Comet wrote:
On Mon, 30 Nov 2015 19:03:55 -0600
-MIKE- wrote:
If you use a phosphoric acid cleaner, like Boeshield Rust Free, there
would be no scrubbing or scraping necessary. Let science to the hard
work.
seems to contradict the instruction from the maker
quote
"Directions. For light rust on steel or cast iron, spray RustFree„¢ on a
rag and wipe surface. Do not spray directly on surface, as it may cause
spotting. For heavy rust, spray directly on rusted surface and scrub
with Scotch-Brite„¢ pad. Wipe off and repeat if necessary. RustFree„¢
works best above 70° F.
CAUTION! RustFree„¢ is acidic and should be used with care.
Test on hidden area before use.
Can cause spotting on cast iron and steel.
Rinse off painted surfaces thoroughly and neutralize with soap and
water. Do not use on guns or black oxide tools.
Can dull paint and plastics.
Not for spot cleaning of table tops.
Do not use on polished cast iron surfaces."
First of all, I was referring to your words, "a putty knife to scrape
away most of the rust
then a wire brush." That's considerably more than simply rubbing the
surface with a Scotch pad. It's akin to 40grit belt sander vs. 220
sandpaper to knock off the nubs from cured lacquer.
Using the Scotch-Brite„¢ pads essentially ensures the acid is getting to
all the rust. I have found it to be unnecessary for about 80% of my
rust removal.
Seriously, rehabbing old power tools is a hobby of mine. Usually when I
get one, whatever metal surface isn't painted with be deeply rusted.
I've tried EVERY technique purported on the internet short of
sandblasting. The only ones that work involve phosphoric acid because
of the chemical and physical reactions it has with rust.
When I first started, I went with RustFree's directions and found the
scrubbing unnecessary. For tough, deep rust, all that is necessary is
to let the product sit a minute or two longer. The reason they tell you
to scrub is the same reason they tell you to NOT use it on polished
surfaces. Because it will cause spotting. The spotting is the acid
somewhat "etching" the metal. Metal workers with use phosphoric acid as
a metal priming technique to give the metal some "bite" for powder
coating. But that's all it will do. It's not an aggressive or
dangerous acid like hydrochloric. That's mostly why they suggest
scrubbing; get it on and get it off quick. It does work fast, by the way.
So, here are the conclusions I came up with for using it.
The places you have deep seated rust on old tools are NOT going to end
up being a smooth polished surface anyway. They are likely cast parts,
that have a rough texture to begin with. Like on a saw: the trunnion,
the underside of the table, etc.
Any parts you that should be smooth, polished surfaces-- like the tables
tops of a saw or jointer, or chisels-- are going to need ground out,
sanded, and polished anyway. So any "pitting," spotting, or etching
done by the phosphoric acid is a moot point, because it'll be sanded out
in the process of smoothing out a polished surface.
--
-MIKE-
"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com
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