hydrochloric acid and blake sea cock

rrees

rrees

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www.cruisinglogs.org.uk
I flushed the scale out of m7y outlet pipes using hydrochloric acid. When I went to pump it out, the pump broke, leaving the acid in the\pipe. Will the blakes sea cock be attacked by the residual acid? I understand that they are made of bronze and as far as I know bronze, being an alloy of copper and tin, should not be attacked by HCl. However, having turned the sea cock off I now have a sklight seepage from between the cone and its seating. As I intend a 2 day crossing to Sicily I don't want a catastrophic failure, but on the other hand I don't want the cost and delay of an unnecessary lift out. Anny ideas?
 
Re: hypochloric acid and blake sea cock

hypochloric or hydrochloric ?? - if the latter then beware !

tin + hydrochloric acid = stannous chloride + hydrogen.
Sn + 2HCl = SnCl2 + H2

don't know about the other stuff.

If you are really nervous then jump overboard and shove a softwood plug (wrap a piece of thin cloth round it first) into the hole from the outside and use a bucket ???

good luck
 
The key to this is what strength of acid was left in contact with the seacock and for how long. If the seacock is below the waterline and was left open, then the concentration inside the cock will rapidly diminish. If, on the other hand, you left a concentrated solution of HCl in the pipe and turned the tap off, there might be a problem.

The biggest risk is not whether the seacock is weeping but whether the casting has corroded internally, causing loss of strength.

Can you describe exactly what you did?
 
Re: hypochloric acid and blake sea cock

[ QUOTE ]
It's hydrochloric acid (HCl) 30%.

So that risks detinning the bronze? I thought tin was fairly inert, like copper.

Thanks.

[/ QUOTE ]

What makes you think that copper is inert - cos it most definitely isnt so.
 
All the pump and seacock makers will advise most strongly against using aggressive chemicals in the system. If you left the stuff in long enough to dissolve the scale I would suspect that you haven't done a lot of good to any of the parts, including seals, seacocks or anything else that made contact with it. If you have recently serviced your Blakes and loaded them up with grease, that might have provided some protection. I never use anything stronger than vinegar and if the pipes are really clagged up there is really no option but to take them off and beat them on the dock to break up the scale or in extreme circumstances, replace the pipe. Since getting into the Med, I have been amazed at the rate of build up. I recently spent the thcik end of an hour chipping off scale and cleaning the inside of our Lavac pump.
 
Doesn't sound as though the vinegar is doing much good. My father used HCl for over 20 years, and I have been using it for over a decade with no apparent ill effects. Concentrated in the bottle, but dilute once it hits the water in the pan, of course. I fill the pan with fresh water, add a couple of teacups of HCl, pump through to empty the pan then leave it, with the seacock open. I think that the concentration of HCl in the seacock must fall very quickly as it is open to the sea. Last time I removed a hose (which I seldom do as HCl keeps the pipes clean) I scraped the bronze and it looked absolutely fine, just like virgin metal, where I had scratched it. Mind you, it was not a lab inspection, it was the best I could do with my head in the bilge section!
 
Well, maybe I'll have to revise my descale programme! The vinegar does get off gungy deposits in the pan and what we might call the U bend, but admit it didn't do much for the Lavac pump, although Blakes are very fierce about using anything more aggressive to clean the system, arguing that it will cause the rubber valves and diaphragms to swell and distort.
 
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