Scale in heads pipes - mechanical or chemical cleaning?

[VicS]

Thread drift ...

At the Boat Show there was a company called Salt Away that claims: "Salt-Away is a selected blend of biodegradable ingredients chosen to provide the best concentration of cleaning materials and chemical agents to remove salt from all surfaces. It also has built in corrosion inhibitors that stop corrosion before it starts."

The MSDS doesn't offer any clues, so what gives?

I know of it. . No idea what it is though.

 

[makingplansfor]

Having replaced all the heads pipework last winter with a rather expensive reinforced rubber pipe I am keen to slow the future build up. When I leave the boat I now flush through with fresh water and dissolve a washing machine descaler tablet (cheap supermarket version of Calgon) in the final few pumps. Sound logic??

 

[Marsupial]

Flush the whole sytem with lots and lots of seawater, then remove pipes - if they're a tight fitagain, fill them with hot water for a while first - beat the pipes against a quay wall, or if at anchor, the bow roller works well; better still, get the missus to do the beating. Give pipes a good rinse in seawater, then refit; once again, if they're a tight fit, just fill them with some hot water.

I've tried brick acid and other commercially available acid based products in the UK and not been impressed with the results; the Turkish Pur-Jus worked well enough - I'm told that is sulphuric rather than hydrocloric acid - it turned my fingers yellow - but even that'll only shift 'moderate' scale build-up and we never remember until it's too late.

The Turkish stuff you mention is nitric acid, so please be careful with it. Anyway, an occasional flush with that or hydrochloric will keep the pipes lime scale free, as others have said if the pipes are almost blocked the chemical process will take some time but it's often easier than removing the hoses to beat them up on a wall somewhere.

 

[skyflyer]

Funny how this 'salt' doesn't dissolve in the seawater in which it is constantly immersed.

Info: The solubility of sodium chloride is only slightly greater in hot water than it is in cold.

My pipes dont look like the above with powdery fine white build up but more a grey, gritty substance like mortar. Pic below is the old piping that we removed last winter

Retarding the chemicals. I dont quite see where the Calcium comes from. Sea Salt contains Sodium (Na), potassium (P)and Chlorine (Cl). Urine will contain Nitrogen (N) and Carbon (C), but cat really see where the Calcium comes from in any great quantity.

I guess it is relevant in that whatever chemical you use needs to be appropriate to what the salt/encrustation actually is.

Any chemists out there?

 

[nigelmercier]

I dont quite see where the Calcium comes from... Any chemists out there?

Vic is our resident chemist, but I'll try to explain. You know that hard tap water has a lot of Calcium, and that it is from dissolved limestone. Well that limestone was formed when there was a sea in the same location...

Sea water contains about 400 ppm of Calcium, with tap water anything above about 200 ppm is considered very hard.

 

[skyflyer]

Thanks

 

[vyv_cox]

Calcium deposition in all seawater systems is a constant problem, although it occurs more rapidly in contact with urine, as VicS has explained. Search 'exhaust elbow' for example. Seawater inlets on rigs we used to run required regular de-scaling.

 

[Neeves]

My pipes dont look like the above with powdery fine white build up but more a grey, gritty substance like mortar. Pic below is the old piping that we removed last winter

Retarding the chemicals. I dont quite see where the Calcium comes from. Sea Salt contains Sodium (Na), potassium (P)and Chlorine (Cl). Urine will contain Nitrogen (N) and Carbon (C), but cat really see where the Calcium comes from in any great quantity.

I guess it is relevant in that whatever chemical you use needs to be appropriate to what the salt/encrustation actually is.

Any chemists out there?

The sea is full of calcium, in solution - all those little creatures on the sea floor, call them 'shell fish' or coral extract that same calcium to form their shells. The White Cliffs of Dover and limestone deposits were formed in seawater and. I believe, in certain parts of the world calcium carbonate is even now being naturally deposited on the sea floor (there being supersaturation (?)). What I fail to understand is why calcium is deposited in exhaust elbows (which as far as I am aware has little contact with urine) and why the deposit gets so hard so quickly. We actually get a build up of calcium scale on the water intake to the engine - so all that is happening is the water is sucked in, no contact with anything (apart from a hose installed with the engine). (For reference - in Sydney, Australia) Its easy to remove (flog it - do not fancy it going through the impellor) but the only chemical reaction can be with the rubber hose (it has the engine manufacturers name on it).

 

[VicS]

The sea is full of calcium, in solution - all those little creatures on the sea floor, call them 'shell fish' or coral extract that same calcium to form their shells. The White Cliffs of Dover and limestone deposits were formed in seawater and. I believe, in certain parts of the world calcium carbonate is even now being naturally deposited on the sea floor (there being supersaturation (?)). What I fail to understand is why calcium is deposited in exhaust elbows (which as far as I am aware has little contact with urine) and why the deposit gets so hard so quickly. We actually get a build up of calcium scale on the water intake to the engine - so all that is happening is the water is sucked in, no contact with anything (apart from a hose installed with the engine). (For reference - in Sydney, Australia) Its easy to remove (flog it - do not fancy it going through the impellor) but the only chemical reaction can be with the rubber hose (it has the engine manufacturers name on it).

there are several ways in which calcium carbonate deposits can be formed

In addition to the route already discussed if can be formed by the thermal decomposition of calcium bicarbonate. That is the way in which scale is formed in heating systems, kettles, engines and probably in the exhaust elbow.

It can also be formed as a result of excessive cathodic protection and is deposited at and around the cathode. Maybe that is the cause of the deposit on the water intake.

There are also marine organisms that form a scale like deposit