Lime Scale removal with hydrochloric acid

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roger

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I've just calculated the amount of acid required to dissolve lime scale and the result was a bit of a shock.
You need about 205 grams of concentrated hydrochloric acid to dissolve 100 grams of lime scale. Bearing in mind that concentrated HCl is very nasty stuff and would probably dissolve any metal in the system it is not a sane way to go.
My heads outlet pipe is divided into two sections by the breather widget. This makes it a bit easier to dismantle for bashing against a wall so this might be a palliative but its still a horrible process to do.
 
Acetic acid is kinder than HCl and easier to work with. It works well on glassware and crockery. You still need a lot for that weight of limescale, but if you leave the pipe in a bucket overnight it won't pose any danger to anyone, and the release of hydrogen will be less vigorous than with conc. HCl!!
 
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I've just calculated the amount of acid required to dissolve lime scale and the result was a bit of a shock.
You need about 205 grams of concentrated hydrochloric acid to dissolve 100 grams of lime scale

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I dont think anyone is suggesting that the things we do with these acids are designed to dissolve all of the limescale, but merely loosen it so that it flushes through.

I would guess that if you have a 38mm pipe reduced to a third of its' diameter by limescale, no amount of our acid treatments will get rid of it.

In fact, my experience suggests that, in a pipe reduced as above, acid treatment is most likely to dislodge some limescale which then blocks the pipe completely.

Starting with a brand new pipe, a weekly flush with say 10% Hcl will probably prevent the build up, and that seems to be the goal.

Prevention, rather than cure, methinks.

Richard
 
Many years ago when I used to descale commercial dishwashers as part of my job we used Phosphoric acid. Very effective and not so nasty as hydrochloric I believe.
 
I have just used Aluminium Cleaner from Machine Mart to descale my sea toilet - I think that the active ingredient in that was phosphoric acid.

worked a treat but I'm not sure how you'd use it on a build up like that - I suggest removing the pipe and knocking it about with a rubber mallet to shift the stuff.

andy
 
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... and the release of hydrogen will be less vigorous than with conc. HCl!!

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er... where does hydrogen (H2) come into the equation(sic)? /forums/images/graemlins/confused.gif
 
An alternative to removing and knocking the pipe about is to subject it to measured compression from a G cramp to crack the scale, then soak in acetic acid or something less insistent than the gunk exuded by the Alien! Better all round I think - just done it, satisfactorily on 10 years' of accumulated scale.

PWG
 
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