What kind of acid?

[nastyjones]

I don't want to subject my old 4-1 to any more sandblasting, it's thin enough as it is. What acid is supposed to remove rust? Muriatic? Hydrochloric? How do I use it? Diluted?

[Steve]

Not sure which acid to suggest, just be aware that acid might take away some metal, too.

.

[old_skool]

Phosphoric acid, home depot in the paint section, called prep and etch, like $15 a gallon.

[Nessism]

Phosphoric acid, home depot in the paint section, called prep and etch, like $15 a gallon.

Yes on the phosphoric acid. Unfortunately, they don't sell anything like being referenced above at my local Home Depots.

Evaporust works great. Oxalic acid works well too (look at the deck cleaner or deck bleach products to see if they contain oxalic acid). Both of these won't eat off good metal while killing the rust.

[1_v8_merc]

Muriatic will etch the metal, in a very short period.
Try Naval Jelly(phosphoric acid), it doesn't smoke and burn holes, lol.

Muriatic Acid contains hydrochloric acid.
(so think of it as the same thing, just two different names)

You can find it in most hardware stores, in the concrete/masonry section.

To neutralize any of these acids, just dillute it with water, and dump some baking soda or washing soda, stir, then let it sit over night...

[AJ]

Muriatic will etch the metal, in a very short period.
Try Naval Jelly(phosphoric acid), it doesn't smoke and burn holes, lol.

Yep, Naval Jelly. Your Home Depot or Walmart will carry that.

[themess]

Muriatic acid is just another name for industrial grade hydrochloric acid. "Industrial grade" doesn't mean stronger. It means less pure than laboratory grades.

If you need to ask what kind of acid to use, please don't use concentrated acids. Phosphoric acid isn't a terribly strong acid, but it can still hurt a person. Naval jelly is about a third the concentration of the normal liquid. Its gelled form makes it a lot less likely to be splashed, which is the major way that people get hurt with it. Naval jelly is also pretty obviously not something to play with. Concentrated phosphoric acid looks a bit like corn syrup.

[DannyMotor]

I've de-rusted the inside of many a moped-frame gas-tank with sulfuric acid. About 10 parts acid to 1 part water mixed in a gallon jug... then poured in... sloshed around... set over night. Drained the next morning, and chased with 3 gallons of BOILING hot water mixed with about 3-4 boxes of baking soda to neutralize it.

If your pipes aren't pitted, you could try the "Evaporust" or "Rust-Mort" products, but those are normally made to neutralize the rust so that you can paint it and it won't begin to bleed through.

I think if you used a spray-bottle of 75/25 Sulfuric Acid to Distilled H2O and gave it a heavy misting, you could probably buff-off the rust in about 30 minutes with a micro-fiber cloth.

*Use gloves
*Wear Eye Protection
*Do not use near painted surfaces

It's basically battery acid... 5 gallons will cost you 15 bucks at an auto parts store.

[nastyjones]

My pipes are quite pitted. That's one of the reasons why I don't want to sandblast & why I want to use an acid.

[JEEPRUSTY]

Evapo rust is a near miracle for rust removal.
No scary thing to worry about.

[old_skool]

Evapo rust is a near miracle for rust removal.
No scary thing to worry about.

Plus if you use a catch container for however you spray it on or submerge parts, you can re-use it over and over again, some even filter it until it quits working. Evapo rust or the prep and etch are your cheapest and very proven methods, prep and etch can be diluted or use at full strength. Use water afterwards to neutralize. No need for concoctions or soda. Also can be used for the inside of a fuel tank, neither will hurt chrome and the P&E wll at the same time coat any bare metal for future rust prevention.

[themess]

...I think if you used a spray-bottle of 75/25 Sulfuric Acid to Distilled H2O and gave it a heavy misting, you could probably buff-off the rust in about 30 minutes with a micro-fiber cloth.

*Use gloves
*Wear Eye Protection
*Do not use near painted surfaces

It's basically battery acid... 5 gallons will cost you 15 bucks at an auto parts store.

FWIW, I've been responsible for chemical safety at several factories.

STAY THE H*LL AWAY FROM SULFURIC ACID. Fortunately battery acid is about a fourth the strength of concentrated sulfuric acid. Aerosol sulfuric acid, even at the concentration used above (1/4 x 1/4 = 1/16th) could fry a person's lungs if inhaled. It is a very strong oxidizing agent, especially when heated.

Never add water to sulfuric acid. (This applies to most concentrated acids, but especially to sulfuric and nitric acids.) The reaction is highly exothermic. Enough heat can be released for the acid to boil - instantly - and cause a glass container to shatter. "Your ass will be grass if you add water to acid." When diluting acids, always add the acid to water, and do so very slowly.

Sufluric acid reacts with iron under some conditions to form hydrogen gas, and at others it forms SO2 gas and HCl gas. Those turn to sulfurous and hydrochloric acids if you inhale them.

Don't use concentrated acids unless you are fully clothed (rubberized aprons are advised). A safety shower and eye wash should be within a few feet.

Forget sulfuric acid and use EvapoRust.

[nastyjones]

Good advice, thanks