TOPIC:

Muriatic acid is generally used for etching concrete and other masonary jobs. Phosphoric acid is generally used for prepping metal... it removes rust and then "deadens" the spots that had been previously rusted. You definitely dilute phosphoric acid... not sure about muriatic acid.

I've used naval jelly to remove rust before, and it seems to me that naval jelly and a fistfull of nuts would do a pretty good job of cleaning rust out of a tank, without the muriatic acid. I guess they wouldn't be using the muriatic acid though unless it was pretty effective in removing rust...

I used the tile and grout cleaner from Home Depot, it is a diluted (25%) solution of phosphoric acid. The tank looked like new inside, and still does today. Probably due to the protective layer that phosphoric acid leaves behind. If you use muriatic the tank may start to rust again at some point.

What's the way to dilute acid? Pour acid into the water, or water into the acid. I keep forgetting...

This site could use an FAQ on some of the basic problems we come across.

Always pour acid into water.
If you pour water into the acid, it may boil or splatter (don't ask).

Hey fergyfer,
First of all muratic acid is just sulfuric acid diluted with four parts of water to one part of acid. I'm not sure how strong a concentration of phosphoric acid Naval Jelly has. So lacking that info I can't judge the realative strength of each. I do know that if I get muratic acid on my skin I generally like to get it off right away but if I get Naval Jelly on my skin I generally don't bother with it till I clean up after the job.

As to whether or not I dilute the muratic acid. I use it full strength. I've found that phosphoric acid will not attack scaly rust very well unless you can get at it to scrub it with a wire brush, something that's difficult at best inside a tank. On the other hand, muratic acid takes scale and rust off quickly. A few steel nuts always help.

I said it before, be careful with any acid. Wear gloves, old clothes and eye and or face protection. For good measure, I like to wash my clothes immediately after handling acid just in case I didn't notice that I splashed on myself.

Glad you folks enjoyed the article. I sure enjoyed writing it.

Bill
KZCSI

Post edited by: kzcsi, at: 2005/12/08 20:24

Thanks for the reply Bill! My plan is to use the muriatic acid full strength, and then dump it into a plastic bucket with water in it. Then to cancel out what's left of the acid, I'll add baking soda to the water before I pour it out. I don't have any spare concrete that I can pour it on... That should work.

One correction to KZCSI's statement:
Muriatic Acid is Hydrochloric Acid (HCl), not Sulfuric (H2SO4).

Hey LT,
Thanks for the correction, you're right of course.
Bill.

del

Been there done that. Try it if you like but as I said the phosphoric won't get the scale off. The phosphoric acid will work best after the muratic acid as it will leave a coating of iron phosphate which is slightly less prone to flash rusting during the drying out process.

KZCSI

I really wish I'd taken before and after photos, but your procedure worked perfectly. My arms could only take 10 minutes of constant shaking of the tank with the muriatic acid and nuts inside, and I was continuously having to re-seal the taped over fuel gauge hole (I apparently didn't get enough of the grease and grime off that area for the tape to seal good) but after 10 minutes I pulled the tape and drained the now brown acid into a bucket of water and flushed and the inside was clean and silver. Before it was brown, scaly and bad enough that I was a little worried that I'd eat through the tank with the acid. I looked with my little dentist mirror and the entire inside that I could see was sliver. I then taped up again and put two bottles of naval jelley in and shook it up good every 30 minutes or so for two hours and rinsed it good. Looks like new inside. By the way, a magnet on a stick really comes in handy getting all the nuts out of the tank after the acid job!
I added a new petcock, fuel filter and rebuilt the carbs. It's a good feeling to know everything is clean!
Thanks KZCSI for the writeup!

NOTE: I wore elbow length rubber gloves, face shield, a full length smock and knee high rubber boots, all of which I highly recommend. Also, after draining the acid into the rubber bucket, I added baking soda to neutralize the acid.

Post edited by: fergyfer, at: 2005/12/12 10:15

While cleaning my RD tank a few years back I found a very helpful item in the local parts store.

I used an expandable freeze plug to block the filler opening. It worked like a charm. Of course, blocking the petcock opening was a bit more of a challenge.

Scozz