Forgive me father for I have sinned

[Fab1]

6 minutes ago, zmk1962 said:

Here's a few thoughts Fab...

Although, sea water is often called salt water and predominantly has dissolved salt (NaCl - sodium chloride - table salt) it also contains other dissolved salts/minerals - such as calcium, potassium, magnesium etc etc. When dissolved in water and allowed to sit they form both acidic and alkaline solutions which will pit the aluminium. 

Pure aluminium is actually very reactive - notice when you cut or scratch aluminium- the exposed fresh surface is very shiny, but quickly dulls - that's the aluminium reacting with oxygen to create an aluminium oxide skin. Aluminium oxide is very inert. This protective layer of aluminium oxide is what gives aluminium it's longevity. May not be the most attractive but it works.

I see how shiny your boat is on the outside -  do you buff it and apply a wax or other protective coat on to keep it shiny?  If not, you are removing a few layers of aluminium atoms off your boat each time!

Agree with this. Hydrochloric is very aggressive -  if it gets into the joints and around welds it could do more damage than good - and you need to consider how you are going to fully flush out the acid. Vinegar or sulfamic acid are much gentler acids.

...not through fibreglass/gelcoat ... that's why they make fibreglass saltwater pools or fix leaking concrete pools with a fglass resin coat !

Hmmm... rubber ducks don't last forever.  My concern with rubber is that you will never again see what is happening underneath it. Even clean water under rubber will become slightly alkaline and eat your hull.

+1 for fish oil or something like it. It's recommended for the inside of trailer box sections etc. Just make sure you get one that "dries" and dries fairly quickly. Some of them form a skin and stay quite wet which maybe be a pain if you ever have to handle your foam blocks. A few of my early cars were treated with fish oil back in the 80s all stood the test of time ...  fish oil is thin, light and liquidy, it will run into crevices and corners a lot better than any rubber compound that I am aware of. 

Cheers Z

PS - have you ever seen a rusty fish?

PPS - the US coast guard and Navy paint alloy vessels below the waterline... and leave them bare above.

https://www.boatingmag.com/protecting-aluminum-boats-from-salt-water-corrosion/

 

  

 

Excellent info mate as always.

My boat has never been polished or waxed.

Some of your concerns I’ve thought about too..

- Not knowing how things are going under rubber I’ve thought about and no longer am going with that for that very reason as I want something I can see so have thought about using perhaps lanolin or silicon spray instead.

I’ve used fish oil in old cars and new ones too and as you are aware it stinks and the tacky ones never dry pretty much.

As for the Hydrochloric acid I’ve used it for decades for heaps of stuff and have loads of it here as I have a fibreglass saltwater pool.(I do all my own maintenance).

  You can buy many ally cleaners in brands like chemtec and septone etc which are alot milder than hydro I’m fully aware.I’ll go with them and see how things go.I’ll dry hull fully with compressed air afterwards and spray lanolin or silicon all over hull and lift floor again in a year after decent use(I’ll be back out soon).

[Fab1]

35 minutes ago, Fab1 said:

There's always one.Believe it or not prior to Covid I would have it out once a week.The key is night fishing so the sun doesn’t degrade it.😂

And I forgot to mention at night I avoid Yowie as he fishes mornings.I hate that man.😂😂

[Fab1]

36 minutes ago, Fab1 said:

There's always one.Believe it or not prior to Covid I would have it out once a week.The key is night fishing so the sun doesn’t degrade it.😂

And I forgot to mention at night I avoid Yowie as he fishes mornings.I hate that man.😂😂

[Yowie]

40 minutes ago, Fab1 said:

And I forgot to mention at night I avoid Yowie as he fishes mornings.I hate that man.😂😂

Use fish oil, you might attract some fish. 

[Fab1]

1 hour ago, Yowie said:

Use fish oil, you might attract some fish. 

Me thinking that’s the key to catch your fish.

[JonD]

My concerns would be first on stopping the galvanic corrosion, finding its cause. This could be wiring, wrong metals used to fix rod holders radios and sounder etc or something as simple as a beer top or sinker under the floor. The quality of the marine grade aluminium has been greatly reduced since we sold most manufacturing out to china. Even builders that do still build in this country often end up using overseas aluminium which has backfired on their reputations.
Personally I would be searching into Galvanic corrosion and try to find someone with expertise to asses your boat rather than experiment cleaning and covering yourself. 

[Fab1]

4 hours ago, JonD said:

My concerns would be first on stopping the galvanic corrosion, finding its cause. This could be wiring, wrong metals used to fix rod holders radios and sounder etc or something as simple as a beer top or sinker under the floor. The quality of the marine grade aluminium has been greatly reduced since we sold most manufacturing out to china. Even builders that do still build in this country often end up using overseas aluminium which has backfired on their reputations.
Personally I would be searching into Galvanic corrosion and try to find someone with expertise to asses your boat rather than experiment cleaning and covering yourself.  

  Cheers mate.

    It’s been caused by salt water sitting in hull under floor and being carried under there when washing/rinsing boat.

  There is no way you can clean under there properly without lifting floor,removing foam,washing,rinsing and drying properly each time she’s in the drink.

  I bought some aluminium cleaner (acid) and have done some testing with good results. I’ll acid wash the hull tomorrow hopefully and spray it with corrosion inhibitor we use at work that’s suitable for ally that works great too.

  I’ll lift floor after a while when I start using it again a dozen times or so and re-evaluate where I’m at.

 As for taking it to someone else I already know what’s causing it.

 Thanks for your help.

[Fab1]

I gave the boat a mild acid wash as I didn’t want to go all out on it for obvious reasons and it’s cleaned up pretty good.I’m in 2 frames of mind wether to spray it with corrosion inhibitor,leave it alone,Leave foam out even though sections with no foam have corroded or what?Can anyone confirm if they’ve ever had a aluminium boat with pits/corrosion like this and if they think spraying it would help?

@JonD I’m starting to think it’s salt which there definitely was dry/caked salt in there combined with electrolysis/galvanic corrosion mate.

I don’t have any dissimilar metals in contact with each other or stray currents as far as I know and am going to go through boat again to check.

 Thanks for everyone’s help.