Tender hull barnicles

[ArranP]

Highfield tender ( hypalon tubes / aluminium hull ) had been sitting in sea water for several months, pulled tender out onto a trailer, scrapped off the barnicles, however some residue from the barnicles still remains that is slightly rough and not possible to scrap off.

Any ideas how to clean this off, some chemical(s) maybe or must it be sandedand repainted ?

Thanks for feedback.

Regards
Arran.

[GordMay]

Barnacles can leave behind a calcium-based residue, known as a husk.
Once the barnacle shells have been removed; use a calcium remover, or a mild acid*, such as oxalic or phosphoric acid, found in hull cleaners, to remove the husks, that don't scrape off.
Apply the chemical to the husks, let it penetrate them, and rinse away with water. A couple of applications, and scrubbing [/w a nylon brush] may be necessary, to remove the husks.
* Sometimes, a stronger acid is required, such as muriatic/hydrochloric acid [HCI].

[ArranP]

Originally Posted by GordMay

Barnacles can leave behind a calcium-based residue, known as a husk.
Once the barnacle shells have been removed; use a calcium remover, or a mild acid*, such as oxalic or phosphoric acid, found in hull cleaners, to remove the husks, that don't scrape off.
Apply the chemical to the husks, let it penetrate them, and rinse away with water. A couple of applications, and scrubbing [/w a nylon brush] may be necessary, to remove the husks.
* Sometimes, a stronger acid is required, such as muriatic/hydrochloric acid [HCI].

Thank you.

[NYSail]

Be careful what you use getting on the pontoons.

[GordMay]

Hypalon has good resistance to acetic [vinegar], oxalic, phosphoric, & hydrochloric acids - but a good fresh-water rinse is always wise, with any use of acid, on any substrate.

[Tin Tin]

Originally Posted by GordMay

Hypalon has good resistance to acetic [vinegar], oxalic, phosphoric, & hydrochloric acids - but a good fresh-water rinse is always wise, with any use of acid, on any substrate.

The HCL on the alloy hull may be a problem though

[GordMay]

Originally Posted by Tin Tin

The HCL on the alloy hull may be a problem though

Indeed.
Aluminum metal will react with dilute* hydrochloric acid, to dissolve, producing aqueous aluminum chloride [AlCl3], and hydrogen gas [H2].
However, this reaction will not take place, as soon as you combine aluminum and hydrochloric acid solution, because the piece of aluminum is protected by a layer of aluminum oxide [Al2O3], due to it’s prior reaction with the air.
The acid must remove this protective layer, before it is able to react with the aluminum underneath.

A “fizzing” noise signifies that the reaction is taking place, as bubbles of hydrogen gas [odourless] are released, and is happening at a rapid rate.
Additionally, there may be some white-coloured smoke, or pungent fumes, coming from the mixture, due to the formation of AlCl3 particles.

* Pour your acid into water, to dilute it. When water and acid mix, a large amount of heat is generated. As long as you pour the acid into a container of water, the heat will be safely dispersed.
If you pour the water into the acid, the initial mixture is very concentrated acid, and it may get hot enough to flash boil.

Remember:

Originally Posted by GordMay

... a good fresh-water rinse is always wise, with any use of acid, on any substrate.