DIY Home Aluminum Anodizing


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  • Masking aluminium anodising

    Anodising aluminium is a fantastic way to form a hard durable coating on machine aluminium parts. You can also make the parts a pretty colour with anodising dyes. What are the disadvantages? Let us address the issue of masking parts in the anodising process.

    Then a part is anodised, we first clean the part in caustic soda. This removes part of the surface of the part. When the part is anodised, the anodised layer is built up on the surface of the part. This actually makes the part larger by a few thousandth of an inch.

    This slight growth is not really much of a problem normally. However, if we have carefully machined a part, for example, to be a slip fit over a shaft, then we do not want that bearing surface anodised.

    To prevent areas of an aluminium part from becoming anodised it needs to be masked. The easiest way for the amateur to mask areas against anodising is to use polyester masking tape.

    Polyester masking tape is used in the painting, powder coating an anodising industry to mask areas of a part that you do not want anodised.

    Polyester masking tape is easily found on Ebay. Try searching for “Masking polyester” – most of the stuff I buy is green coloured and comes in a roll which is 10mm wide for about £6.50. This tape also stands temperatures up to about 220C, so it will not come off unless you roast your part in an oven!

    The polyester anodising masking tape is simply applied in the areas we want to mask from the anodising process. This can be quite a fiddly job in hard to reach areas, but take your time and make sure the tape is will glued onto the surface. Make sure the part is clean and free of moisture or grease before trying to use the masking tape!

    Another use of anodising tape is to mask of areas after the anodising process but before dying. This allows us to make multi coloured anodised aluminium parts.

    a roll of polyester anodising masking tape aluminium part ready for anodising with polyester masking tape parts anodised and dyed with masked area showing

    In the photos above we can see a large reel of polyester anodising masking tape. I have applied some to the central bore of a part before anodising. After anodising we can see that the central bore is untouched by the anodising process.

    Masking with polyester powder coating masking tape is an effective way of stopping selected areas of the part from becoming anodised.


    Contact me on tomh at tomh@tomhow.me.uk

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