While battling a small crack in a cast aluminium exhaust manifold I developed a keen interest for two component epoxy glues and putty`s. Seeing as the weldability of that particular cast aluminium was about 0, I had to find an alternative way to keep the cooling liquid in it`s place. I tinkered around with a few of JB weld, and loctite products and a few questions came to mind:
- Should the worck piece be heated before applying the epoxy? One could argue that the heat would make the material open up and give a stronger bond. On the other hand, the material expansion might make the crack you are trying to fill up smaller. In the case of an exhaust manifold I theorize that normal working temperature would make the crack bigger. and crack any epoxy that is not flexible
- What is the optimal curing temperature? Most epoxy products demand a good 24 hours to cure completely. It is well known that heat speeds up curing time, but a few seasoned mechanics have told me that it also makes it weaker and more penetrable. If so, where is the optimal tradeoff between time needed and integrity of the finished product?
- How should you prepare the surface for maximum adhesion? My way of doing it has been to first clean the area with rag and aceton. Removing any stubborn contaminants with scotch brite pad, before roughing up the surface with a 40 grit sanding paper. Could one have better results with using something even coarser? Making scrapes and ridges with something sharp?
- Is it wise to apply several thin layers with a few hours in between, or is one thick layer just as good?
- Do the products become weaker the more heat resistant they are? If you look at youtube and project farms testing of different products. JB weld`s high-, and extreme heat products only have a fraction of the strenght of what the original cold weld product achieves.
- Is there any way to disclose a products strength and elasticity just by looking at ingredients and spesifications?
- What solvents destroy cured epoxy? Will it outlast us all?