Anodised Aluminium options?

[vamoose]

I'm wondering what experiences/opinions others have in regards to choosing a type and method of anodising (plain or black (or coloured)) on different aluminium components in stirling engine designs. Also what type or level of finish, prior to anodising, is best suited in regards to optimising thermal transfer? Note that the surfaces I’m referring to for my design, will Not be in contact with piston seals or rubbing surfaces, and wont be in contact with flames, although some surfaces may have to endure temperatures of up to 200 deg Celsius (or potentially hotter)...

vamoose

[Ian S C]

There is a bit of discusion on anodising on the model engineering website at the moment. For the cold end this would be the ideal finish as it becomes part of the metal, unlike paint that may look nice, but actually slows the cooling rate (or peals off), and acts as an insulator. You don't ask, and I don't know how its done, but hard anodising is good on aluminium pistons, or it can be used on the bore of cylinders, Briggs & Stratton, and others use it, and this or the teflon treatment of aluminium is the only way I would use aluminium for pistons. Ian S C

[rustybarrel]

Hi
I was reading about anodising aluminium the other day. From what I got to know is this. Hard anodising is done with a dilute solution of sulphuric acid ( dilute than used for normal anodising) but with the solution temperature maintained at 2 - 4 degree C. I think it will be a costly affair to do at home or at small scale. As for the solution strength and other paramerets you can google it yourself if you are so interested.