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And another for what it's worth,don't let any sit in an open container,it will give a surface coat of rust to anything within six feet or more and thats a fact !!

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Six feet? LOL! I wish it was only six feet. I left a plastic watering can with a smidgen left in the bottom in my garage over night (I had cleaned my driveway with it). The fumes flash rusted EVERY bare piece of metal in my garage, including the entire stripped front clip of my '72 Satty. I had already blasted the trunk floor and front floor pans too...yup, flashed. Pissed me off so bad I haven't touched the Satty in months and I'm now selling it. All that work sand blasting with a Harbor Freight blaster with about an inch wide spread, just to have it all flashed in a single night.

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Stay safe and be sane.

Number 1. Using acid to remove dirt, oil, and gunk is poor workmanship and a bad choice of methods. Better to use your wife's dishwasher with hot water and strong ammonia-containing soap or some other effective cleaning method.

Number 2. Insert only clean objects free of dirt, oil, and rust scale in a de-rusting chemical to preserve the strength and effectiveness of the chemical. It's a waste of the chemical to dissolve rust scale and cut oils that could have been easily removed.

Number 3. If you are trying to restore a piece of metal, generally speaking HCl is overkill and way too corrosive and unsafe. If the piece being restored has spot welds, HCl left in the cracks can keep on corroding and pop the welds. Something a lot less potent, such as vinegar or Evapo-Rust will get the job done effectively and safely. Yes, one of these is not cheap, but if you use good workmanship and follow Number 2 above, you won't waste it.

Number 4. Remove any object from any rust removing chemical immediately as soon as de-rusting is accomplished.

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If I neutralize the acid bath after use, it too should contain dirt, oil, water and bits of metal right? So shouldn't this qualify as acceptable to dump in the used oil dump at the parts store?

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No. The metals/metal oxides and dirt is not the problem. (It would also contain salts, but again they would not be a problem either.) The reason why is because it only contains a small amount of oil (hydrocarbons) and a lot of water in the solution. As we all learned in grade school science classes, oil and water will not mix, they separate into layers given enough time (unless acted upon by detergents, which interacts with both layers). Where the layers sit depends upon the densities of the materials. Recycling companies do not want to mess with used oil that has been contaminated with large quantities of water and not properly separated. If you separated (ie. decanted off) the oil layers from the cleaning process and disposed of them in the used oil recycling container, that is fine. But, you cannot just dump all of the aqueous solution in there as well. You will become liable for the disposal costs if you do so. Open your wallet wide if that happens....

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Now HF will kill you. It is both a strong acid and very very toxic, and will absorb into the body on contact through your skin. H2SO4 can also be considerably more dangerous than HCl, depending on concentration.

I'm all for doing the right thing, but today's hysteria over everything being toxic is simply mis-information. In our 5 second sound bit society, we don't even bother with the details of science.

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Stay safe and be sane.

Number 1. Using acid to remove dirt, oil, and gunk is poor workmanship and a bad choice of methods. Better to use your wife's dishwasher with hot water and strong ammonia-containing soap or some other effective cleaning method.

Number 2. Insert only clean objects free of dirt, oil, and rust scale in a de-rusting chemical to preserve the strength and effectiveness of the chemical. It's a waste of the chemical to dissolve rust scale and cut oils that could have been easily removed.

Number 3. If you are trying to restore a piece of metal, generally speaking HCl is overkill and way too corrosive and unsafe. If the piece being restored has spot welds, HCl left in the cracks can keep on corroding and pop the welds. Something a lot less potent, such as vinegar or Evapo-Rust will get the job done effectively and safely. Yes, one of these is not cheap, but if you use good workmanship and follow Number 2 above, you won't waste it.

Number 4. Remove any object from any rust removing chemical immediately as soon as de-rusting is accomplished.

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1. It's not a bad method. It's just a method.
2. The whole point of the acid bath was to remove dirt oil and rust.
3. Driving a car is unsafe. Having sex is unsafe. Flying in a plane is unsafe. playing football is unsafe. All one can do is to be as safe as possible doing any of these things, and it's no different when using chemicals to clean metal, wood, or anything else. Also, the parts Im dipping have no welds.
4. Agreed.

From now on I will be neutralizing my acid when finished. I dont mind disposing of it at the dump's hazardous chemical hut. But there is also a free oil dump at one of the local parts stores. In this oil dump, you can dispose used motor oil that is full of carcinogens, metals, dirt and water.

If I neutralize the acid bath after use, it too should contain dirt, oil, water and bits of metal right? So shouldn't this qualify as acceptable to dump in the used oil dump at the parts store?

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Bold text: Your not doing it right

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Number 1. Using acid to remove dirt, oil, and gunk is poor workmanship and a bad choice of methods.

1. It's not a bad method. It's just a method.

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Now HF will kill you. It is both a strong acid and very very toxic, and will absorb into the body on contact through your skin. H2SO4 can also be considerably more dangerous than HCl, depending on concentration.

I'm all for doing the right thing, but today's hysteria over everything being toxic is simply mis-information. In our 5 second sound bit society, we don't even bother with the details of science.

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HF (hydrofluoric acid) is actually a weak acid (pKa = 6.8X10^-4), but it can etch (ie. digest) glass. [The larger the pKa value, the more it will ionize in water which leads to its acid strength via the formation of the hydronium ion, H3O+(aq).] Hydrofluoric acid is used as such in glass/mirror shops, although they tend to favor the active paste salts in usage. H2SO4 (sulfuric acid) is stronger than HF because it can ionize in solution to approximately 100% ions. So, each molecule of H2SO4 generates 2 molecules of hydronium ions in water. HNO3 (nitric acid) can also ionize 100%, as well as the dreaded HClO4 (perchloric acid). I do not handle perchloric acid unless I absolutely have to, as it can eat flesh to the bone (even after flushing with copious amounts of water) unless neutralized with the right base. It also forms explosive metal perchlorate salts upon contact with nearby metal surfaces. Only those who are properly trained in safely handling such materials should be using said materials in the first place....

Yes, chemicals tend to get a bad reputation in the media. One thing I teach in my chemistry classes is that there are no "bad" chemicals. It all depends on how they are being used and why. The key to the message is to not fear chemicals (as the media would like), but to respect what they can do by learning about them....

If you do not know how to handle a certain chemical, it is better to leave it to the professionals who do....

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Nuke 1, I'm certainly not a chemistry teacher but I have worked with these things daily for 38 years. To say that HF acid is weak may be misleading to those reading this. It is the most dangerous to humans of any listed here so far (nitric is close), such that even our drivers have to carry calcium gluconate to transport factory sealed drums of it. Exposure without treatment can lead to death within 24 hours or so. So perhaps "weak" as in ability to eat things but "lethal" as in human contact might be a better description? Again, not trying to split hairs here, just trying as always to keep members from getting hurt or worse.

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HF (hydrofluoric acid) is actually a weak acid (pKa = 6.8X10^-4), but it can etch (ie. digest) glass. [The larger the pKa value, the more it will ionize in water which leads to its acid strength via the formation of the hydronium ion, H3O+(aq).] Hydrofluoric acid is used as such in glass/mirror shops, although they tend to favor the active paste salts in usage. H2SO4 (sulfuric acid) is stronger than HF because it can ionize in solution to approximately 100% ions. So, each molecule of H2SO4 generates 2 molecules of hydronium ions in water. HNO3 (nitric acid) can also ionize 100%, as well as the dreaded HClO4 (perchloric acid). I do not handle perchloric acid unless I absolutely have to, as it can eat flesh to the bone (even after flushing with copious amounts of water) unless neutralized with the right base. It also forms explosive metal perchlorate salts upon contact with nearby metal surfaces. Only those who are properly trained in safely handling such materials should be using said materials in the first place....

Yes, chemicals tend to get a bad reputation in the media. One thing I teach in my chemistry classes is that there are no "bad" chemicals. It all depends on how they are being used and why. The key to the message is to not fear chemicals (as the media would like), but to respect what they can do by learning about them....

If you do not know how to handle a certain chemical, it is better to leave it to the professionals who do....

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Nuke 1, I'm certainly not a chemistry teacher but I have worked with these things daily for 38 years. To say that HF acid is weak may be misleading to those reading this. It is the most dangerous to humans of any listed here so far (nitric is close), such that even our drivers have to carry calcium gluconate to transport factory sealed drums of it. Exposure without treatment can lead to death within 24 hours or so. So perhaps "weak" as in ability to eat things but "lethal" as in human contact might be a better description? Again, not trying to split hairs here, just trying as always to keep members from getting hurt or worse.

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Now HF will kill you. It is both a strong acid and very very toxic, and will absorb into the body on contact through your skin. H2SO4 can also be considerably more dangerous than HCl, depending on concentration.

I'm all for doing the right thing, but today's hysteria over everything being toxic is simply mis-information. In our 5 second sound bit society, we don't even bother with the details of science.

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HF (hydrofluoric acid) is actually a weak acid (pKa = 6.8X10^-4), but it can etch (ie. digest) glass. [The larger the pKa value, the more it will ionize in water which leads to its acid strength via the formation of the hydronium ion, H3O+(aq).] Hydrofluoric acid is used as such in glass/mirror shops, although they tend to favor the active paste salts in usage. H2SO4 (sulfuric acid) is stronger than HF because it can ionize in solution to approximately 100% ions. So, each molecule of H2SO4 generates 2 molecules of hydronium ions in water. HNO3 (nitric acid) can also ionize 100%, as well as the dreaded HClO4 (perchloric acid). I do not handle perchloric acid unless I absolutely have to, as it can eat flesh to the bone (even after flushing with copious amounts of water) unless neutralized with the right base. It also forms explosive metal perchlorate salts upon contact with nearby metal surfaces. Only those who are properly trained in safely handling such materials should be using said materials in the first place....

Yes, chemicals tend to get a bad reputation in the media. One thing I teach in my chemistry classes is that there are no "bad" chemicals. It all depends on how they are being used and why. The key to the message is to not fear chemicals (as the media would like), but to respect what they can do by learning about them....

If you do not know how to handle a certain chemical, it is better to leave it to the professionals who do....

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Nuke 1, I'm certainly not a chemistry teacher but I have worked with these things daily for 38 years. To say that HF acid is weak may be misleading to those reading this. It is the most dangerous to humans of any listed here so far (nitric is close), such that even our drivers have to carry calcium gluconate to transport factory sealed drums of it. Exposure without treatment can lead to death within 24 hours or so. So perhaps "weak" as in ability to eat things but "lethal" as in human contact might be a better description? Again, not trying to split hairs here, just trying as always to keep members from getting hurt or worse.

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It's so much easier to use electrolysis.

Have a battery charger?
Have a piece of scrap metal?

Grab a tub and some washing soda. Plug it in and make it work.

Just don't use stainless steel as an anode.

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