VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Muriatic Acid

Chipper,

Regarding last week's thread on the use of muriatic acid as a rust remover, I respect your degree in chemistry. I have used muriatic acid with good results and would like to try cleaning out the cooling system passages in the block and head of my 216 engine. The head has 8 copper nozzles pressed into it which guide the coolant stream toward the exhaust valves. Is the muriatic acid going to eat the copper nozzles?

Mark Yeamans
VCCA #35724

Mark,
If you dilute to ~ 3 % (dilute 1:10) or less it will not be too aggressive toward anything in the cooling system of older cars. It will remove the copper salts (mostly oxides) on the surface of the copper tubes and redeposit the copper metal on the exposed iron surface. That will not be a problem.

If there is any aluminum, zinc, diecast, white metal or similar metal the acid will dissolve it! Only modern cooling systems normally have those type metal.

If you do a search you should find a description of my recommended procedure to use muriatic acid to clean the cooling systems of our older Chevys. I use it routinely to clean cooling systems. Just did a '51 a few weeks ago.

CAUTION before using any hazardous chemical be sure you read and understand the precautions and handling information contained on the Material Safety Data Sheet (MSDS) or alternately (but not as good) the container label. Also understand how to dispose of any chemical safely and in an environmentally acceptable manner. That includes the waste from its use.

Years ago you used to be able to get a cooling system flush kit that contained oxalic acid.

Yes oxalic acid flush formulas were common 20+ years ago. The use of aluminum radiator cores doomed all acid based (chemists inside joke?) cooling system cleaners. They had a few advantages in that they also helped to remove hydrocarbon (grease and oil) contamination. Alas us old car fogies don't present enough business for the vast majority of suppliers. Fortunately we have the Filling Station, Chevs of the 40s, Carter and others that cater to our needs. Also the online chat sites help to disseminate a bunch of good information on DIY options.

And Chipper, not tryin’ to be a troublemaker here, it’s just my nature to be full of questions. And that is always the question that comes to mind when ever I hear a discussion on Oil, antifreeze, acid etc. How do you dispose of it properly? The only answer that I ever seem to find is what's printed on the package, "Dispose of this product in the proper manner", but that doesn’t tell me a thing about what the proper manner is?? I'm not a chemist and have always been afraid to use acids. I tend to shy away from things that I know can hurt you if I don’t thoroughly understand them. I mean, I have filled batteries when they used to come dry and I have done some anodizing using battery (sulfuric) acid but that’s about the limit of it. I do remember hearing something about neutralizing acid by mixing in baking soda?? Is that the proper way to dispose of it, I mean is it rendered harmless if you mix baking soda into it??
The engine oil, hypoid oil, kerosene I use in the gunk tank and anything that will burn, I’ve manage to find a diesel shop that has a couple of 500 gal drain oil tanks that they recycle for their oil burner furnace. The anti-freeze waste I still haven’t been able to find any way of getting rid of it, and I better pretty soon cuz I’m got a bunch of it stored.
So bout that acid???
Denny Graham
Sandwich, IL

First if you don't understand the hazards, disposal, handling of any chemical (that includes almost everything that is not food) get a copy of the MSDS. All chemicals, mixtures, blends, etc. have them! I know I helped write a bunch of them. If you request a MSDS when you purchase a chemical product they are required to provide it or help you get one. Most are written so the basic information can be understood by most people. If you don't understand there will be contact information to get more or help to understand what is in there. The MSDS contains handling, hazard, first aid, disposal, toxicity information.

The best method to properly dispose of antifreeze, drain oil or other similar products is to take them to the outlet that sells that product. Most will take back the waste and process it according to EPA standards. Same with batteries. If they will not take it back consult your local fire department. They are trained to handle hazardous spills and disposal. They may not have the specific information but can lead you to someone that does.

It is best to use the criteria, "If you don't understand how to do it right then don't do it."

What most people don't understand is that the oil you drain from your engine contains in addition to the oil, heavy metals, acids and other hazardous materials. Same for antifreeze. Burning the oil will produce an ash that still has those heavy metals so it must be disposed of properly. Though not 100% accurate if any material in what you are disposing has ever been classified as hazardous the entire contents are considered hazardous and regulated as such. It is almost impossible to process a hazardous waste into one that is deemed non-hazardous. The possible savior for us consumers is that there are minimum levels that are not considered hazardous.

All this gives me a headache.

Phosphoric acid is, in my experience, less aggressive and easier to control than Muriatic. For general rust removal, typically mix 3 parts water to 1 part acid.

There are major differences between phosphoric and muriatic acids and their effectiveness in removing rust and hard water deposits even though both are mineral acids. One is that phosphoric can have a greater impact on the environment. In addition you might consider two organic acids, acetic and citric. Both of them are less aggressive and hazardous than the mineral acids. You might consider one of them too.