Announcement

Collapse
No announcement yet.

Deoxidising "Aluminium"

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Deoxidising "Aluminium"

    I have some modern coach lamps outside the house. They're only a few years old, but the paint has fallen off and they have grown coats of white furry oxide. I say aluminium - it's probably some nasty alloy, what is sometimes referred to as muckmetal. They're die cast. Some alloy of aluminium / zinc / magnesium? I don't know what it is, but I'm pleased they don't make aircraft wings out of it.

    Most of the paint has flaked off, the rest will come off either by a bit of scraping or paint stripper for any stubborn bits. Is there an easy method of getting the white furry corrosion stuff off, or does it still come down to wire brush & sandpaper?

    Thanks,

    Ian
    All of the gear, no idea...

  • #2
    mechanically would be safest, sodium hydroxide (lye) would be the simplest and most effective. Make up a 5% NaOH solution (add the base to the water), warm it up a touch and put the pieces in for 30s to a minute at a time. Do this outside as the fumes are nasty. This will strip back any and all oxides to bare metal and leave a uniform dull finish.

    Comment


    • #3
      Thanks Matt,

      I'll try to find a source of sodium hydroxide. I live in the Netherlands, where anything more toxic than salty water is banned!

      Ian
      All of the gear, no idea...

      Comment


      • #4
        A strong solution of laundry bleach and detergent will also work just a bit slower... maybe with some scrubbing... sodium hydroxide is one of the main ingredients in laundry bleach. Also in certain drain openers.

        Comment


        • #5
          Look at the gootsteenontstopper ingredients. Some are pure NaOH. Be very careful with it, don't get any on your skin as you'll get severe chemical burn.

          Comment


          • #6
            Blasting, will get it off, beadblasting etc.
            just for kicks try a pressuremwasher or car wash.

            Comment


            • #7
              Your coach lights may be made of a cast zinc alloy, I've had door hardware that was cast zinc react to the alkalinity if the mystery
              core ( a stone composite of some sort like cement boards ) of the door and the symptoms were blistering paint and fuzzy white oxides.
              Best bet is mechanically abrade the oxides off.

              Comment


              • #8
                Originally posted by nickel-city-fab View Post
                [...]... sodium hydroxide is one of the main ingredients in laundry bleach. [...]
                Chlorine bleach is sodium hypochlorite.

                Comment


                • #9
                  Originally posted by Bob Engelhardt View Post

                  Chlorine bleach is sodium hypochlorite.
                  According to the Clorox company, the ingredients are:
                  Water
                  Sodium Hypochlorite
                  Sodium Hydroxide
                  Sodium Chlorate
                  Sodium Xylene Sulfonate


                  ... so yes it does seem like there's sodium hydroxide in there. And yes, bleach does eat aluminum and other white metal products, being strongly alkaline.

                  Comment


                  • #10
                    Originally posted by Ian B View Post
                    Thanks Matt,

                    I'll try to find a source of sodium hydroxide. I live in the Netherlands, where anything more toxic than salty water is banned!

                    Ian
                    I know in the US most drain cleaners are sodium hydroxide based, dunno if that holds true in the netherlands though. In a pinch though, you could make heated solution of baking soda and water that might have the same effect if you dip your parts

                    Comment


                    • #11
                      Alumi-prep /Acid etch and alodine

                      then prime and paint

                      Comment


                      • #12
                        If you even think that it is aluminium, DO NOT use sodium hydroxide as it will dissolve the aluminium. If you must, try it on small hidden part first, As others have said, sodium hydroxide is often the main ingredient in drain cleaners - it is also referred to / sold as 'lye' or 'caustic soda'. Add the powder to water slowly as it gives off quite a bit of heat as it dissolves.

                        Comment


                        • #13
                          Thanks for that everyone! The drain cleaner we get here has little shavings of metal (aluminium?) in it, along with the white crystals. I could certainly give that a try. If it doesn't work, at least I then get nice clean drains

                          I think JCFX is right - they'll be made of a zinc alloy. Considering the mess of immersing the bits in liquid, I might just go at them with sandpaper...

                          Ian
                          All of the gear, no idea...

                          Comment


                          • #14
                            Originally posted by CalM View Post
                            Alumi-prep /Acid etch and alodine

                            then prime and paint
                            where can i get alodine? e.g. alodine 1200s/bonderite m-cr 1001? do you have 100g you could let me have? (powder, that is.)

                            Comment


                            • #15
                              if you dont want the lye to eat up the aluminum, use a sulfuric acid solution. hydrochloric for zink.

                              Comment

                              Working...
                              X