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Old 22-05-2019, 03:23   #1
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Scale growing on aluminium water tank

We are requiring assistance with an aluminium water tank in our Grand Banks 47 - 2010 year of manufacture. The aluminium water tank is 503 grade, manufactured by Talsco in engineering Singapore. The thickness of the tank is 4.5mm.

We were alerted to the problem because of a very noisy water pump and the fact that we were continually replacing the water pump because of pressure switch. In opening the inspection ports we have found as per the following photos, a granule type scale growing on all surfaces. We are concerned regarding the safety of drinking the water. If you have any suggestions to rectify and clean tanks we would welcome any advice.

Kind regards
Proud GB owner
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Old 22-05-2019, 03:36   #2
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Re: Scale growing on aluminium water tank

this is quite common in aluminium tanks that have not been painted with zinc chromate,then barrier coat.
probably aluminium oxide and calcium/mineral deposits.
keep the tanks full as the aluminium needs air to oxidise,you could try putting a magnesium anode in the bottom of the tank.
steam clean,pump out and clean out debris with wet n dry vacuum
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Old 22-05-2019, 05:29   #3
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Re: Scale growing on aluminium water tank

Greetings and welcome aboard the CF, Brad.
I think atoll gave you some good advice. Also, pay close attention, if Peggie Hall weighs in.
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Old 22-05-2019, 05:54   #4
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Re: Scale growing on aluminium water tank

Steam won't help since heat does not matter in this case. High pressure water is fine.



The Mg anode seems smart. I'm interested in hearing if there is a reason this might not be a good idea. Aluminum toxicity is occasionally debated, but not Mg (unless you overdose on supplements).
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Old 22-05-2019, 09:15   #5
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Re: Scale growing on aluminium water tank

use a solution of 50/50 white vinegar and water fill tank and leave for a day then rinse. repeat if necessary then as often as needed or replace the tank
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Old 22-05-2019, 09:39   #6
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Re: Scale growing on aluminium water tank

It's caused by Chlorine. I don't put any chlorinated water in my tanks unless its an emergency. RO water only.
Also don't use a descaler not meant for aluminum.
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Old 22-05-2019, 09:48   #7
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Scale growing on aluminium water tank

I would not ever paint anything that contained drinking water and or food with zinc chromate, itís a known carcinogen, has been for a long time, and in fact is now hard to get.
https://toxnet.nlm.nih.gov/cgi-bin/s...rm+@DOCNO+6188
We stopped using it to manufacture aircraft when we reopened the plant in 02.

My aluminum waste tank was obviously I believe epoxy coated, you could tell cause it looked like it was full of egg shells when you emptied it.

I wouldnít coat it with anything, in fact Iíd leave it alone, maybe the magnesium anode, but there shouldnít be that type of corrosion, but why not protect anyway?

I have an aluminum water tank, circa 1987 and I know itís a matter of time before it fails, itís not if, itís when.

I filter very slowly every drop of water that goes into my tank with a carbon block charcoal filter, look for one that is called a carbon block, and look for it to be made from coconut wood, filter slowly because the charcoal needs a dwell time, if you pump water at 50 PSI though it, its not going to get as much chlorine as if you let it go through slowly.
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Old 22-05-2019, 10:15   #8
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Re: Scale growing on aluminium water tank

A chemist relative of mine, when I had the same problem in a previous boat, told me not to worry regarding any health issues, but to simply add a cup of vinegar and leave overnight. It worked perfectly. The water had a slightly vinegar taste for a day or two, (not harmful) and things I washed in it, like pots and pans, came out cleaner than ever. Never had the problem again, but was completely confident in both the tank and the remedy.
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Old 22-05-2019, 11:00   #9
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Re: Scale growing on aluminium water tank

I have had the same issue since aluminum boats usually have built in water, fuel and waste tanks. After cleaning out the deposits I put in vinegar and let sit for a few days before rinsing. I also put in magnesium anodes. We will see if they do the job.
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Old 22-05-2019, 11:00   #10
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Re: Scale growing on aluminium water tank

Quote:
Originally Posted by contrail View Post
A chemist relative of mine, when I had the same problem in a previous boat, told me not to worry regarding any health issues, but to simply add a cup of vinegar and leave overnight. It worked perfectly. The water had a slightly vinegar taste for a day or two, (not harmful) and things I washed in it, like pots and pans, came out cleaner than ever. Never had the problem again, but was completely confident in both the tank and the remedy.
we have very large aluminium tanks,that are integral to the hull,2 drinking water tanks,2500 liters were treated/sprayed with a very thin solution of zinc chromate to etch the metal then epoxy primer coated,no corrosion after 20 years.
our rainwater tank that is about 1000 liters and is bare aluminium and gets emptied regularly,which looks similar to the OP's photo

in the past we have used phospheric acid to etch the aluminium which removes the oxide deposits,as would vinegar.

exposure to air soon starts the process again of oxidation which is how unpainted marine grade aluminium ultimately protects itself from corrosion,as the surface corrosion only continues untill a layer of oxidation has formed,this then protects the metal from further corrosion.

in uncoated water tanks, the aluminium oxide gets dissolved in the water when the tanks are filled and slosh about,then has to re oxidise when the tank gets exposed to air again as they are emptied to replace the layer of protective oxide removed in solution ,and so on the cycle continues till the wall is eventually eaten through
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Old 22-05-2019, 12:34   #11
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Re: Scale growing on aluminium water tank

Hello,
With aluminium tanks, no chlorine, no kind of water treatment based on silver. Every thing will eat your tank. Put a fine filter between the tank and the water pump. Clean it one or two time in the year. Use a fine filter (like Seagull IV or other) for drinking water.
Good sailing.
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Old 22-05-2019, 13:18   #12
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Re: Scale growing on aluminium water tank

We've a friend with an old aluminum French boat. When he fills his water tanks, he pre-filters out the chlorine from the local water supply. He has two large charcoal filters he runs the water through (household size). His tanks do not have the scale the OP photographed, since he cleaned them and instigated his pre-filtering program.

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Old 22-05-2019, 23:15   #13
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Re: Scale growing on aluminium water tank

I would never drink water stored in aluminium or cook in aluminium pots it is almost impossible to eliminate from your body even with chealation I have tried
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Old 23-05-2019, 05:27   #14
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Re: Scale growing on aluminium water tank

Quote:
Originally Posted by PEACEMAKER 455 View Post
I would never drink water stored in aluminium or cook in aluminium pots it is almost impossible to eliminate from your body even with chealation I have tried


How do you test for aluminum in your tissues?
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Old 23-05-2019, 13:28   #15
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Re: Scale growing on aluminium water tank

Hi I have aluminium tanks on my boat and found that desalinated water caused this white chalky substance and normal water was no problem.We spent 5 years cruising asia NG and pacific islands.
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