I want to make a part using molten aluminum with a hole through the middle and would like to use a steel rod to do this. Would the bar stick to the aluminum when it cools and not be able to be removed? If so is there so type of coating I can use so it can be removed?
Aluminium and iron are pretty incompatible materials, they don't form an alloy I don't think, so it is unlikely they would stick. Also, both metals will get an oxide layer on the surface which should keep them separate. Try it! If the finished part does stick, try heating the aluminium then dip the steel rod in some ice water.
Unless the surface was specially prepared the aluminum won't bond to the steel. To be sure it doesn't, simply 'smoke ' the steel with a candle etc. (thin layer of carbon black), to ensure no bonding. Your problem will come from the different co-efficients of expansion. The aluminum will shrink more than the steel in cooling and will grab that rod very tightly. Your hole, ( therefore your rod), will have to have a considerable taper if you ever hope to drive that rod out of the casting. Caution- You are aware that most aluminum alloys will burn in air at pouring temperatures aren't you?
