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Will oxalic acid affect my aluminium handrails and posts???

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  1. #1
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    Default Will oxalic acid affect my aluminium handrails and posts???

    Hi everyone,

    My deck build is almost complete and I need to plan on how to clean/prepare my deck for oiling.

    It is a spotted gum deck with aluminium roof and handrail posts.

    If I use oxalic acid to clean the deck and the top of the handrails, will the acid negatively affect the metal?

    The alternative to this is to use Napisan/sodium percarbonate solution and clean the deck, however I am not sure if this will get rid of all the stains/mill glaze(???) on the deck - will it?

    Reading through the "Cleaning and Oiling Your Deck" sticky had me initially thinking of the Napisan route, however as the thread progressed, oxalic acid was introduced as step 2 of a process (if i didn't want to sand my deck).

    Can anyone shed light on this please?

    20210527_162335.jpg20210527_162406.jpg

  2. #2
    4K Club Member Marc's Avatar
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    Oxalic acid reacts only with oxidised metal so you will be cleaning the bare aluminium as well. That is what is in the aluminium polish you buy, among other things.
    As for the need to use oxalic on new timber... well ... I live that to the more experienced one. I don't think I would bother personally.
    Science is never settled,
    it advances one funeral at the time.
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  3. #3
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    Thanks Marc. I thought i was going to need to wrap all the aluminium in some sort of plastic before applying oxalic acid. Having said this, i am considering sticking with Napisan/Aldi product instead.

  4. #4
    Community Moderator phild01's Avatar
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    Quote Originally Posted by jojujove View Post
    Having said this, i am considering sticking with Napisan/Aldi product instead.
    Save money and buy the cheap no brand sodium percarbonate in the laundry aisle.

  5. #5
    4K Club Member Marc's Avatar
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    Sodium percarbonate, that is washing soda and peroxide, unless it has added sodium metasilicate to prevent aluminium and copper corrosion, is a bad choice.
    I suggest you make a strong solution of the product you intend to use and dip a few pieces of aluminium foil in it to see how it behaves.
    Alcalies strip the aluminium of it's protective oxide and react with the metal. Oxalic acid only reacts with the oxide not the metal.
    Of course you could brush a bit of oil/wax solution on the aluminium as a temporary protection
    Science is never settled,
    it advances one funeral at the time.
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  6. #6
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    Thanks. The posts are coated/painted except for the areas that were cut/drilled. That should in theory provide protection to the aluminium (I think).

  7. #7
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    Quote Originally Posted by Marc View Post
    Sodium percarbonate, that is washing soda and peroxide, unless it has added sodium metasilicate to prevent aluminium and copper corrosion, is a bad choice.
    I suggest you make a strong solution of the product you intend to use and dip a few pieces of aluminium foil in it to see how it behaves.
    Alcalies strip the aluminium of it's protective oxide and react with the metal. Oxalic acid only reacts with the oxide not the metal.
    Of course you could brush a bit of oil/wax solution on the aluminium as a temporary protection
    I ended up wetting everything then giving the deck and handrails a wash with oxalic acid (diggers rust and stain cleaner). Washed everything down again after I was done. Black metal marks gone. However there seemed to be new black marks once things dried out. Will hit them with oxalic acid. I was supposed to oil the deck but it is raining and will continue to rain tomorrow so that isn't happening.

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