[ChrisVDC]

Please excuse me, I have not taken chemistry since high school.  I am reteaching myself as best I can.

So I work for a company that involves lead-acid batteries.  The big problem with failures is from PbS04 crystal formation.  I read that NH4Cl is excellent at dissolving PbSO4.

Pb Pb02 PbSO4 H2SO4 H2O H3O H O are all present in a standard battery, sometimes even more elements if they use lead alloys. Plus the plastics of the enclosure.

So I read that NH4Cl will combine with H2SO4 and form HCl.  And that HCl will react with Pb and form PbCl and H.

First off, is this dangerous?  Am I missing something that will product Cl gas?

Secondly, would this work in terms of dissolving the lead-sulfate? Or will the other reactions happen first using up the NH4Cl?

Thirdly, would this ruin the battery functionally?

I am guessing that there is a downside, as people would be selling it as a battery additive like they do MgSO4 and CdSO4.

Thanks for your patience.
 

[jeffrey.struss]

So I read that NH4Cl will combine with H2SO4 and form HCl.  And that HCl will react with Pb and form PbCl and H.
 

Balancing the equation (2HCl + Pb --> PbCl2 + H2). Mean you get hydrogen gas. That is a VERY bad thing.

[ChrisVDC]

Hydrogen gas is a normal byproduct of lead-acid battery charging, so I guess it depends on the quantity we are talking about.  Say if it removes enough hydrogen from the system to stop the normal charge/discharge reactions from occurring, then it would be pointless.

Also pointless if this all happened before the sulfate was dissolved.

I am trying to figure all this out, taking some time.  If you could help me understand it a little more in depth I would appreciate it.

Thank you.

[jeffrey.struss]

I think the difference is in volume over time. When charging it produces small amounts of hydrogen gas which may be big over time but are small in amount at any point in time.. 50g of NH4Cl will produce roughly 22L of gas, more than likely pretty rapidly at that. Chemical reactions that produce a gas tend to be really favorable both entropically and in driving the reaction rapidly (because of LeChatlier's principle and the removal of a the gas means the removal of a product).

[AWK]

_{Balancing the equation (2HCl + Pb --> PbCl2 + H2). Mean you get hydrogen gas. That is a VERY bad thing.}

Pb rather does not react with HCl

Very dangerorus for life and for battery is reaction
PbO₂ + 4HCl = PbCl₂ + Cl₂ + 2H₂O

[ChrisVDC]

Ah, that would be the kind of thing I was very worried about.

The Cl2 produced, it will be in enough quantity to come out of solution?

How come the HCl does not react with the Pb?

[Enthalpy]

Adding anything to a battery is a bad idea, if it isn't a well-known and documented method.

Batteries are difficult to make, the improvement you suggest would be long known if it brought something. Lead batteries have been around for well over a century.

You noticed? Users are supposed to pour only de-ionized water in a lead battery, because nearly any impurity is detrimental.

In short: don't.

[mcdonabe]

The electrochemical potential for the reduction of pb(IV) is much greater than oxidation of Pb(0) with HCL, so that reduction of Pb(IV) is favored ( although, idk if this is what awk was referring to in saying that the latter reaction does not happen).