Phosphoric acid. Dilution ?

[oldgit]

Intend to give my raw water system a flush out, no problems but one engine temp is now slightly up by a degree or two.
In the past have used Wickes Brick cleaner in various dilutions to shift the crud, with excellent results.
Chum recently used Rydlyme and was happy with the stuff.
However being a tightwad decided to buy 5l of Phosphoric Acid via ebay for about 1/3 the price of Rydlyme and see what the results are.
Simple job on my engines, might just soak or poss flush with a little pump.
The question is.......what strength of solution should be used.

Phosphoric Acid Descaler Rust Remover 45% Safe On Metal Surfaces - 5L

 

[Fr J Hackett]

Intend to give my raw water system a flush out, no problems but one engine temp is now slightly up by a degree or two.
In the past have used Wickes Brick cleaner in various dilutions to shift the crud, with excellent results.
Chum recently used Rydlyme and was happy with the stuff.
However being a tightwad decided to buy 5l of Phosphoric Acid via ebay for about 1/3 the price of Rydlyme and see what the results are.
Simple job on my engines, might just soak or poss flush with a little pump.
The question is.......what strength of solution should be used.

Phosphoric Acid Descaler Rust Remover 45% Safe On Metal Surfaces - 5L

Phosphoric acid is really a rust stabiliser which can then be washed away rather than a dissolver of calcium deposits which are the most likely things blocking the cooling channels although it will do that as well. At 45 % it should be OK to use as is or if you prefer dilute with water 50:50 to give a 22% solution. Unless it is rust you are treating then a dilute hydrochloric acid solution as in brick cleaner would be a better bet.

 

[Plum]

Intend to give my raw water system a flush out, no problems but one engine temp is now slightly up by a degree or two.
In the past have used Wickes Brick cleaner in various dilutions to shift the crud, with excellent results.
Chum recently used Rydlyme and was happy with the stuff.
However being a tightwad decided to buy 5l of Phosphoric Acid via ebay for about 1/3 the price of Rydlyme and see what the results are.
Simple job on my engines, might just soak or poss flush with a little pump.
The question is.......what strength of solution should be used.

Phosphoric Acid Descaler Rust Remover 45% Safe On Metal Surfaces - 5L

Rydlyme contains hydrochloric acid diluted up to 10% (their sds says 5 to 9%), same as the Wickes brick cleaner i use to clean propeller. Not sure what phosphoric acid will achieve.

Www.solocoastalsailing.co.uk

 

[oldgit]

Rydlyme contains hydrochloric acid diluted up to 10% (their sds says 5 to 9%), same as the Wickes brick cleaner i use to clean propeller. Not sure what phosphoric acid will achieve.

Www.solocoastalsailing.co.uk

Thanks.
Might just stick with a quick flush using Wickes Brick.

 

[lw395]

Phosphoric should work fine to dissolve calcium carbonate based deposits.
Dilution is not critical, but if you don't put enough in, it will all be neutralised.
If you leave it in there a while and then check it still fizzes on concrete, it's dissolved everything it's going to. If it doesn't fizz, there probably more chalk to dissolve.

 

[KeithH]

I dont think that it is a good idea to try to use phosphoric acid to remove calcium deposits - as calcium phosphate is insoluble in water. After all, that is what bones are made of!

Hydrochloric acid or one of the acids used in removing lime scale for kettles (eg formic) would be more effective on lime scale.

 

[Fr J Hackett]

I dont think that it is a good idea to try to use phosphoric acid to remove calcium deposits - as calcium phosphate is insoluble in water. After all, that is what bones are made of!

Hydrochloric acid or one of the acids used in removing lime scale for kettles (eg formic) would be more effective on lime scale.

Depending on the form and acidity I think you will find that it is, soluble that is. A mute point because as you say hydrochloric acid is much better at dissolving insoluble calcium deposits.

 

[oldgit]

Tried over weekend .
Scraped a few barnicules off a handy mooring pile and did a quick test in bucket.
Lots of instant fizz,left for an hour or two.Foamy mess but still the odd bit of barnicule remaining in bottom of bucket.
Released a couple of hoses and with a funnel and some very Heath Robinson piping poured in 5L of undiluted Phospheric into raw water pump end of the heat exchanger using gravity.
Lots of fizzing from the outlet pipe going to riser.
Left for a couple of hours.
On the test run temp reduced by about 2-3 degress, not as dramatic as hoped but noticable improvement.

 

[VicS]

Thanks.
Might just stick with a quick flush using Wickes Brick.

Tried over weekend .
Scraped a few barnicules off a handy mooring pile and did a quick test in bucket.
Lots of instant fizz,left for an hour or two.Foamy mess but still the odd bit of barnicule remaining in bottom of bucket.
Released a couple of hoses and with a funnel and some very Heath Robinson piping poured in 5L of undiluted Phospheric into raw water pump end of the heat exchanger using gravity.
Lots of fizzing from the outlet pipe going to riser.
Left for a couple of hours.
On the test run temp reduced by about 2-3 degress, not as dramatic as hoped but noticable improvement.

Fernox DS-3 limescale remover might be a good choice. It is sulfamic acid based

 

[Plum]

Fernox DS-3 limescale remover might be a good choice. It is sulfamic acid based

How does sulfamic, hydrochloric and phosphoric compare in their performance at dissolving limescale?

Www.solocoastalsailing.co.uk

 

[VicS]

How does sulfamic, hydrochloric and phosphoric compare in their performance at dissolving limescale?

Www.solocoastalsailing.co.uk

Hydrochloric acid is a "strong acid" , one of the 3 common strong acids, the others being nitric acid and sulfuric acid.

Phosphoric acid is usually classed as a weak acid although stronger than most with the notable exception of oxalic acid.

Sulfamic acid is a moderately strong acid although not as strong as hydrochloric acid by a long way.

 

[Fr J Hackett]

Hydrochloric acid is a "strong acid" , one of the 3 common strong acids, the others being nitric acid and sulfuric acid.

Phosphoric acid is usually classed as a weak acid although stronger than most with the notable exception of oxalic acid.

Sulfamic acid is a moderately strong acid although not as strong as hydrochloric acid by a long way.

The term strong is often misunderstood and misused in relation to acids.

 

[Hydrozoan]

I have not checked the thermodynamic calculations, but this Wiki section with tables on calcium carbonate solubility in a strong or weak acid solution (including phosphoric) may be of interest: https://en.wikipedia.org/wiki/Calcium_carbonate#Solubility_in_a_strong_or_weak_acid_solution)

(I have given before my view, which seems to be confirmed there, that the maximum amount at equilibrium of CaCO3 that can be dissolved by a weak monoacid, like acetic, is likely to be essentially the same (at the same molarity) as with a strong monoacid - though the reaction will be much faster with the strong acid. And I suspect that the calculation there may not include complexation of Ca2+ ion by the acetate anion, which would I think increase the solubility.)

 

[Fr J Hackett]

I have not checked the thermodynamic calculations, but this Wiki section with tables on calcium carbonate solubility in a strong or weak acid solution (including phosphoric) may be of interest: https://en.wikipedia.org/wiki/Calcium_carbonate#Solubility_in_a_strong_or_weak_acid_solution)

(I have given before my view, which seems to be confirmed there, that the maximum amount at equilibrium of CaCO3 that can be dissolved by a weak monoacid, like acetic, is likely to be essentially the same (at the same molarity) as with a strong monoacid - though the reaction will be much faster with the strong acid. And I suspect that the calculation there may not include complexation of Ca2+ ion by the acetate anion, which would I think increase the solubility.)

Stop concussing people

 

[Hydrozoan]

Stop concussing people

Sorry - but not (e.g.) to you or Vic or Richard, obviously. Anyway, I think the Wiki tables are clear enough about the equivalence of the strong and weak acids in terms of amount of CaCO3 dissolved, even to a non-chemist.

 

[lw395]

How does sulfamic, hydrochloric and phosphoric compare in their performance at dissolving limescale?

Www.solocoastalsailing.co.uk

I think that's only half the question.
The other half is 'and not destroying the metal thing we are trying to clean?'

How d oes the optimum choice of acid vary according to the metals involved?
How does that chnge if there's a mix of metals?
Is a short sharp shock of strong acid better for the metals than long immersion in weaker acid?