We were working on a job the other day and the masons were cleaning
the brick with muriatic acid. The guys doing the work were clever
enough to remove a very expensive front door but in doing so, the wind
blew in a fine mist of acid into the great room where a contractors
saw was set up. Now we have a nice collection of acid "freckles" on
the saw top.
The first thing we could think to do was to see how many finish nails
we could shoot at the masons. After much discussion with my partner
(it is his saw) we eventually decided against that.
Then, we tried cleaning the top with WD 40 and the wiped it down with
Top Coat. The next day the freckles were still growing. Does anyone
have any ideas on how we might neutralize the acid to at least stop
any further deterioration of the top?
Any suggestions would be appreciated!
You didn't specify if the saw table was aluminum or ferrous metal
but ferrous metal should not be eaten away by hydrocloric acid
so I assume aluminum.
To neutralize an acid use a base. But don't leave any long-term
residue on the saw because aluminum reacts with both acids and
I suggest a mild base like baking soda, sprinkle it on, rub it
in, brush as much of it off as you can dry, then wash with a
Do not use sodium hydroxide, it reacts vigorously with aluminum.
OK. Iron exposed to air oxidises to form FeO which is a hard
black oxide that adheres well to the underlying metal. It is
that oxidation that causes shiny iron to fade to its familiar
grey color. Muriactic acid will react with that:
2HCl + FeO -> H2O + FeCl2
So the acid has etched away the patina and left Ferric Cloride.
You will have to use water to wash off the FeCl. Leaving clorides
on the surface will promote corrosion. By now all of the HCl will
have either reacted or evaporated. Exposure to water will further
oxidise the FeO to Fe2O3 the familiar reddish-brown flakey rust.
That in turn can be (should be) rubbed off with fine sandpaper,
steel wool, synthetic steel wool, or a brass brush like a pot brush.
Pretty sure. Muriatic (hydrocloric) acid can be used to clean
scale and mineral buildup in iron pipes. It should not eat
holes in iron overnight.
OP says the table top was cast iron. Perhaps the spots were
discolored, but not pitted?
Muratic acid (which is diluted hydrochloric acid) will damage iron and
steel. In this case it also removed any protective coating that was on the
table and allowed rust to form and keep forming. Phosphoric acid can be use
to remove the rust if you don't want to use an abrasive method. Neutralize
with baking soda or a detergent. Rinse with water then coat with paste wax.
On 14 Sep 2005 01:47:14 -0700, email@example.com wrote:
That's right. It will take a lot less than overnight. It needed to
be dealt with immediately. Used to remove scale, it is meeting the
scale first, and is dilute. It will certainly react with the iron
when it gets there and if continued, and will not take overnight.
When Muriatic [Hydrochloric] acid is spilled, the best solution is a
ton of water ...applied immediately. Otherwise, it's too late.
Applying soda is after the fact. One company kept a bucket of soda
handy for sulphuric acid spills on workers. I advised them to replace
it with a shower head. The acid would cause a sore wound, then they
would rub salt into it. The solution is to flush it out ...quickly
If someone is worried about their spoiled table top, it can be
weld-filled, then machined again. There are at least four small
businesses here who could do that easily.
You could go a little stronger than the baking soda by using ammonia.
If the spots don't go away, you could get gutsy and wet the whole table
down with an even coat of muriatic acid, let it etch its magic, and
then neutralize again.
It would probably be prudent to run this on a sacrificial piece of
Rust Free is a cast iron cleaner product based on Hydro-fluoric acid (nasty
stuff!). Its sold by the same company that sells Boeshield T9 protectant.
They sell the two together as a cast iron cleaner and maintenance system.
Both are available at Woodcraft. I know that the Rust Free stuff does a
good job of cleaning. But if you don't followup with T9 pretty quick, your
table is guaranteed to rust overnight.
You might try some T9 or even clean the top with rust free and then followup
Just checked my Rust Free label. Phosphoric acid is listed as the active
ingredient. Not so nasty. We use it in the janitorial industry to as an
alternative to hydrochloric acid for removing water deposits from steel,
chrome, tile, masonry etc. If it gets on your skin just rinse it off. No
need to even hurry.
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