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Old 10-18-2008, 03:46 AM
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Dealing with battery acid damage

I've always thought that the proper way to deal with battery acid is to neutralize it with a mix of baking soda and water...when the bubbling stops, the acid is gone.

My question/concern is if baking soda causes rust? I don't know how baking soda reacts with steel, but I know from brushing my teeth with it, it tastes like it's at least part salt.

My thinking is if I clean my rust-damaged battery tray with baking soda (prior to wirebrushing/grinding), the baking soda solution is sure to creep down into the cracks, seam welds, etc. If I grind before the baking soda treatment, then there's going to be a lot of acid-soaked rust dust flying around. Am I worried for no reason? How best to deal with this?

Lastly, I guess this question is somewhat related to the various phosphoric acid rust treatments. The usual procedure says to "neutralize" the acid after treatment, usually with a rinse with fresh water. How can plain water neutralize an acid? Is rinsing enough? I searched a bunch and the only reference I found to using baking soda in this situation is from a post by "grouch" here:
secrets of surface rust removal revealed

Thoughts or comments greatly appreciated.

Thanks, Scot

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Old 10-18-2008, 06:44 AM
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I would just rinse it with water. Water will neutralise any acid if enough water is used, it's just a matter of getting the pH value up to 7 or neutral. Soda will neutralise the acid because it is alkaline but is probably not necessary here and will also have to be washed of with water. Battery acid is a relatively mild acid and quickly loses it's acidity when it reacts with anything outside the battery, so it is likely that the small amount of acid you had on your tray is now just water anyway.

Last edited by scrimshaw; 10-18-2008 at 06:50 AM.
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Old 10-19-2008, 01:31 AM
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I agree with scrimshaw about rinsing with water. Your tap water is likely going to be slightly acidic (from absorbing carbon dioxide), or slightly alkaline (from chlorination), but it will be far closer to neutral than either baking soda or battery acid.

I disagree with scrimshaw in characterizing battery acid (sulfuric acid) as "relatively mild" -- that stuff is very dangerous and should be very respected, just like you'd respect a cobra's bite! It'll eat cardboard boxes, steel, skin, eyes and lungs.

See NIOSH Pocket Guide to Chemical Hazards.

I'd rinse the tray with water, dump some baking soda (sodium bicarbonate) on it, scrub it around a bit, then rinse well.

Try this thought experiment. Take an ounce of -stuff- and dissolve it in a gallon of water. Ratio of water to stuff = 128:1. Dump it, assuming 1% stays behind (that's not realistic, but let's say you don't dump very well), or 1.29 ounces of solution. That's .01 ounces of -stuff- and 1.28 ounces of water after 1 rinse. Rinse with one gallon again and you have, roughly, a ratio of 128:0.01. Dump it, again assuming 1% stays behind. Now you have 1% of .01 or .0001 ounces of -stuff- left behind.

I know you didn't ask about that, but your question reminded me of sermons preached at me in chemistry class: Rinse once with a lot and you have a lot. Rinse multiple times with a little and you leave little. Might come in handy someday.
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Old 10-19-2008, 07:34 AM
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Quote:
Originally Posted by grouch
I disagree with scrimshaw in characterizing battery acid (sulfuric acid) as "relatively mild" -- that stuff is very dangerous and should be very respected, just like you'd respect a cobra's bite! It'll eat cardboard boxes, steel, skin, eyes and lungs.
Didn't mean to disrespect Sulphuric acid, you are right of course it is a dangerous chemical so let me clarify.

There are different levels of Sulphuric acid -- the liquid in a battery in a discharged state is just water, the liquid in a fully charged battery is about 30% sulphuric acid, fertilizer can contain twice this and that concentrated acid that we used to play around with at school is about 95% and is highly reactive to many things especially with water. I remember dropping a teaspoon of water into a bowl of it and causing such a violent reaction it broke the bowl, that stuff you treated very carefully, gloves and goggles even when handling the closed bottle.

Contrast this with batteries and how we pour water into them all the time and generally handle them without serious precautions. I worked on a boat that had a huge bank of about 20 large batteries that were positioned so it was impossible to see into them, I would dip my finger into them to see if they had enough electrolyte, rinsed my finger in water straight after of course (how I love gell cells).

But you are right it should be treated with care when you handle it.

As a footnote here one of the largest users of sulphuric acid is the auto industry who use it to remove rust and mill scale from rolls of sheetmetal before using it in car bodies!
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Old 10-19-2008, 10:53 AM
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Fellows I fought the battery acid contamination problem for years on mine equipment (there I go with the mine equipment again , but it is relevant here) on metal a heck of a lot thicker than body sheetmetal. What I found is no amount of rinsing, or pressure washing, will stop the damage from continuing and once the metal is that contaminated replacement is about the best solution. The problem with acid is not just having the corrosive substance lying on the surface dissolving the metal but the fact that once contaminated a chemical reaction is started that is very hard to stop! The acid will "eat" into the metal and cannot be simply rinsed off nor is it easy to neutralize for the same reason. If you can grind deep enough to remove all the contaminated metal you can stop it from getting worse but with the thin body sheetmetal you simply would not have anything left. I have seen it destroy 1/8" thick metal even after taking steps to clean and then neutralize the acid so the only way to completely eliminate the problem is replace the contaminated metal.


Phosphoric acid does not have to be neutralized but for proper adhesion of primer, etc it must have the excess and residue rinsed off but the reaction from it is desirable not harmful. I think one of the problems when dealing with acids is in thinking that "acid" is a chemical itself and that different "acids" are just varying strengths of the same thing. Actually the different kinds of chemicals we know as acids are very different chemicals with very different properties that just happen to be corrosive and different acids can have very different effects on metal.
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Old 10-19-2008, 11:41 AM
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Quote:
Originally Posted by As a footnote here one of the largest users of sulphuric acid is the auto industry who use it to [I
remove[/I] rust and mill scale from rolls of sheetmetal before using it in car bodies!
This is a process used in the steel industry known as "pickling" and the acid solution they use does not even come close to battery acid. This consists of a dip in the relatively weak acid solution and then a rinse immediately after. This has little or nothing to do with getting battery acid on body sheetmetal for even a short time never mind leaving it long enough to do damage such as found with a leaking battery. Another problem to consider is where else besides where you can see did the acid go? How about seams and overlapped parts? Under bolt and screw heads? There is a tremendous difference in full strength battery acid contaminating finished body parts and a a long sheet of new steel being fed through a dilute acid and rinse process in a controlled environment.
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Old 10-19-2008, 02:53 PM
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Like old red says once it starts look out, we have a fleet of busses at work and even rinsing the battery boxes every day or so they still don't last very long.
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Old 10-19-2008, 03:01 PM
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Itís impossible for sulfuric acid or any acid to continue a chemical reaction ad infinitum with a finite source of acid. For example, in the case of sulfuric acid and iron, once one molecule of iron and one of acid react - hydrogen gas is given of and Ferrous sulfate is left behind, when all molecules react there is no acid left.

HOWEVER --- one of the properties of Sulfuric Acid makes things much worse. It is not only part water but also Hygroscopic which means it will soak more water up like a sponge. If you leave concentrate acid in an open container it will soak up so much water that it can double in volume but at the same time will become diluted. This means that when battery acid is spilt on to a painted metal tray, while it will immediately start attacking the paint and etching away the metal, it is pulling moisture in with it and as we know etched metal is heaven for rust. So after the source of acid is taken away and the acid has neutralized the rust is deeply ingrained everywhere the acid was and the rusting begins.

It is an accepted method in industry to neutralize dilute Sulfuric acid i.e. anything below 70% IIRC with water although often soda and other alkaline substances are used depending on time, strength of acid and circumstances. This does not apply to concentrate which will react violently with water.

BTW I wasnít comparing battery acid with pickling; I just found it ironic that the initial stages of the body construction involved sulfuric acid on steel. Also donít forget somewhere in-between a fully charged battery and a discharged one lays the same strength sulfuric acid as the pickling solution. Although I think due to environmental concerns the auto guys have stopped using it.
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Old 10-19-2008, 05:00 PM
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Water dilutes sulfuric acid. A base will neutralize sulfuric acid.

I operated an industrial waste water treatment facility for 8 yrs.
Our process used 94% sulfuric acid (will eat stainless steel, we used Kynar piping))injected at a ratio of 1500 to 8000 ppm into a water based media heated to 225f (1.0-1.5 pH). That mixture was eventually neutralized with lime (12pH). The residue left behind was sludge, with a neutral pH, and the water was a neutral pH water.

We had no stainless steel piping or vessels after the neutralization process which occurred in a cement vessel. Sulfuric acid eats cement very effectively, but with the injected lime causing a neutralizing, there was no degradation of the cement or the black iron piping from that point on in the process.

The solution for pollution is not dilution, do it correctly and neutralize it, then thoroughly rinse and dry the part and epoxy prime.

btw, pure acid has no pH, water is required to be present to have pH.
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Old 10-19-2008, 05:17 PM
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Quote:
Originally Posted by Old Fool
Water dilutes sulfuric acid. A base will neutralize sulfuric acid.

I operated an industrial waste water treatment facility for 8 yrs.
Our process used 94% sulfuric acid (will eat stainless steel, we used Kynar piping))injected at a ratio of 1500 to 8000 ppm into a water based media heated to 225f (1.0-1.5 pH). That mixture was eventually neutralized with lime (12pH). The residue left behind was sludge, with a neutral pH, and the water was a neutral pH water.

We had no stainless steel piping or vessels after the neutralization process which occurred in a cement vessel. Sulfuric acid eats cement very effectively, but with the injected lime causing a neutralizing, there was no degradation of the cement or the black iron piping from that point on in the process.

The solution for pollution is not dilution, do it correctly and neutralize it, then thoroughly rinse and dry the part and epoxy prime.

btw, pure acid has no pH, water is required to be present to have pH.
I vaguely remember that very concentrate sulfuric acid can be kept in regular steel containers -- is that right and how does that work?
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Old 10-19-2008, 11:13 PM
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Thanks for the replies...this is turning into a far more interesting discussion than I had imagined.

My main concerns were the seams and hidden areas where, I'm sure, the acid has dripped into over the years. The acid is definately in there so I was thinking that if residual acid was stuck in there after cleaning, that wouldn't be good. If I used baking soda and some remained in the seams, that also would be a potential problem. Seems like a lessor of two evils type of situation.
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Old 10-20-2008, 10:19 AM
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Quote:
Originally Posted by scrimshaw
Itís impossible for sulfuric acid or any acid to continue a chemical reaction ad infinitum with a finite source of acid. For example, in the case of sulfuric acid and iron, once one molecule of iron and one of acid react - hydrogen gas is given of and Ferrous sulfate is left behind, when all molecules react there is no acid left.

HOWEVER --- one of the properties of Sulfuric Acid makes things much worse. It is not only part water but also Hygroscopic which means it will soak more water up like a sponge. If you leave concentrate acid in an open container it will soak up so much water that it can double in volume but at the same time will become diluted. This means that when battery acid is spilt on to a painted metal tray, while it will immediately start attacking the paint and etching away the metal, it is pulling moisture in with it and as we know etched metal is heaven for rust. So after the source of acid is taken away and the acid has neutralized the rust is deeply ingrained everywhere the acid was and the rusting begins.

It is an accepted method in industry to neutralize dilute Sulfuric acid i.e. anything below 70% IIRC with water although often soda and other alkaline substances are used depending on time, strength of acid and circumstances. This does not apply to concentrate which will react violently with water.

BTW I wasnít comparing battery acid with pickling; I just found it ironic that the initial stages of the body construction involved sulfuric acid on steel. Also donít forget somewhere in-between a fully charged battery and a discharged one lays the same strength sulfuric acid as the pickling solution. Although I think due to environmental concerns the auto guys have stopped using it.



I agree with what you are saying however I think we are talking about two different things. My point is the acid "eats" into the metal, that is it literally becomes part of the metal surface, and as long as any of it remains the reaction will continue. The problem is because of how the acid is in a state of fused contact with the metal it cannot be simply rinsed away with water nor is it easy to neutralize for the same reason. Metal that is corroded from contact with Sulfuric acid would need a layer several thousandths thick removed in order to get all the acid damaged metal out and with body sheetmetal being as thin as it is there simply is not enough there to allow removal and still leave enough for ample strength. If we were talking about exposure of only a few minutes then I would agree that a water rinse followed by a neutralizing agent would do the job but not after substantial corrosion has started, the acid is simply ingrained too deep. The mining equipment I mentioned had serious damage (this was common) from the acid even after pressure cleaning and using chemicals specifically used for neutralizing battery acid however the damage would still continue until the area became so weak it would have to be replaced and this was metal 1/8" thick! We tried everything from baking soda to the special preparations made just for this purpose and nothing worked (we did not know about POR15 at the time, I have to wonder? ) so if 1/8" metal will not survive I seriously doubt that any amount of rinsing with water will stop corrosion from acid damage on metal as thin as body sheetmetal!
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Old 10-22-2008, 12:39 AM
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oldred,
Thanks for the info. Somewhat discouraging, but good to know.
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Old 10-22-2008, 06:42 AM
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Quote:
Originally Posted by oldred
I agree with what you are saying however I think we are talking about two different things. My point is the acid "eats" into the metal, that is it literally becomes part of the metal surface, and as long as any of it remains the reaction will continue. The problem is because of how the acid is in a state of fused contact with the metal it cannot be simply rinsed away with water nor is it easy to neutralize for the same reason. Metal that is corroded from contact with Sulfuric acid would need a layer several thousandths thick removed in order to get all the acid damaged metal out and with body sheetmetal being as thin as it is there simply is not enough there to allow removal and still leave enough for ample strength. If we were talking about exposure of only a few minutes then I would agree that a water rinse followed by a neutralizing agent would do the job but not after substantial corrosion has started, the acid is simply ingrained too deep. The mining equipment I mentioned had serious damage (this was common) from the acid even after pressure cleaning and using chemicals specifically used for neutralizing battery acid however the damage would still continue until the area became so weak it would have to be replaced and this was metal 1/8" thick! We tried everything from baking soda to the special preparations made just for this purpose and nothing worked (we did not know about POR15 at the time, I have to wonder? ) so if 1/8" metal will not survive I seriously doubt that any amount of rinsing with water will stop corrosion from acid damage on metal as thin as body sheetmetal!
Hi Oldred

I think I will have to remain in disagreement. All I have learnt in Chemistry tells me Sulfuric acid because it is so unstable cannot remain on steel that is exposed to the atmosphere without reacting with it, and once it reacts then it is too late to deal with the sulfuric acid but we now have to deal with the damage that it has done. But regardless of the tech. stuff (or wether we are talking about two different things) the end result is the same and I totally agree with you that the damage done is major and deep, and is like giving rust a shot of nitrous, it starts with a vengeance and is hard to stop.

Just an afterthought on the mining experience, was it a Coal Mine you worked in? Coal is very rich in sulfur (acid rain) and most mines in general are cold damp places, I am not suprised you had trouble with corrosion.

Scot

If you decide to repair and not replace, after the cleaning, grinding and rinsing, one of the main things I would do is to make sure that ALL the water is gone especially if I was in Hawaii (you lucky b....). I would do this with a propane torch or heat gun, even a hairdryer is better than nothing, then I would paint with epoxy immediately after it cools.

How about a sealed battery next time!

Last edited by scrimshaw; 10-22-2008 at 08:09 AM.
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Old 10-22-2008, 07:04 AM
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Thanks for the encouraging words. I will give it a shot...clean up and epoxy and will definately take your advice re. drying it out with a heatgun.

Since I grew up here, I love it and can't bring myself to leave. There are major downsides to living out here. The big sore spot for me right now is I can't get SPI epoxy.
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