- Location
- Texas
So in a recent thread discussion about epoxy filling, some Members used steel epoxy (JB Weld) while some recommended using aluminum epoxy like Devcon.
Seems like having like/similar metals would make sense, but does this make thermal expansion sense? As in the epoxy filling/patch expanding and contracting in harmony with the aluminum casting...
Lets start with the fact that the Aluminum coefficient of thermal expansion (CTE) is about 24 x 10 to the -6 power per degree; I will just use 24 to keep things simple. So we want the epoxy filling/patch to have a CTE as close to 24 as possible, that way it expands and contracts in synch with the Aluminum casting as much as possible thereby reducing cracking and flaking.
Steel has a CTE of about 12 and Epoxy Resin has a CTE of about 50. So the CTE of the Steel Epoxy Resin mixture will end up with a CTE somewhere lower than 50, but higher than 12, because the metal will help to lower the CTE and make it more stable.
Then, Aluminum plus Epoxy will end up with a CTE somewhere between 24 and 50. And Steel plus Epoxy will be somewhere between 12 and 50.
Assuming the same amount of metal is added to each epoxy mixture, which mixture will have the lowest CTE closest to the Aluminum Casting?
The Steel Epoxy mixture will have the lower CTE. So JB Weld Steel will perform better than Devcon because it has a lower CTE, thus more stability and strength. And JB Weld is so much cheaper.
What say you?
Seems like having like/similar metals would make sense, but does this make thermal expansion sense? As in the epoxy filling/patch expanding and contracting in harmony with the aluminum casting...
Lets start with the fact that the Aluminum coefficient of thermal expansion (CTE) is about 24 x 10 to the -6 power per degree; I will just use 24 to keep things simple. So we want the epoxy filling/patch to have a CTE as close to 24 as possible, that way it expands and contracts in synch with the Aluminum casting as much as possible thereby reducing cracking and flaking.
Steel has a CTE of about 12 and Epoxy Resin has a CTE of about 50. So the CTE of the Steel Epoxy Resin mixture will end up with a CTE somewhere lower than 50, but higher than 12, because the metal will help to lower the CTE and make it more stable.
Then, Aluminum plus Epoxy will end up with a CTE somewhere between 24 and 50. And Steel plus Epoxy will be somewhere between 12 and 50.
Assuming the same amount of metal is added to each epoxy mixture, which mixture will have the lowest CTE closest to the Aluminum Casting?
The Steel Epoxy mixture will have the lower CTE. So JB Weld Steel will perform better than Devcon because it has a lower CTE, thus more stability and strength. And JB Weld is so much cheaper.
What say you?
