Not my solution but it works. Obviously just the flat bit and it keeps the whole piece in shape. I also glued some thin Ikea fleece blanket to the bottom of the Al to stop it rattling against the steel.
Yeah Richard will no doubt sort you out.
3M Panel bond in its variants is industry standard in automotive certainly, and also aviation to my knowledge. In fact I'll be bonding my aluminium bonnet scoop using the stuff when I get around to it. The stronger versions are even aerospace grade I believe
I used a polysulphide two part sealant (and aviation product), because it sticks to anything & it's flexible. Expensive though. For a one part compound, I'd use something from the Sikaflex line. They used to do a polysulphide, but I think these days Sika just do polyurethane compounds.
I would use one of the MS polymer products or hybrids. Stixall, Fixall, CT1, HB40 - Tradeseal HB40 White - £5.21 +VAT : Trade Grade Products Ltd - The Glue People, Innovation in Adhesion or other. These adhesives do bond very well to such things as PVC and aluminium, but they do need moisture to cure. Best way to use them between two impervious surface like these, is to apply a thin coat to both sides with a serrated glue applicator, then using a spray bottle, just puff some water into the air and let it settle onto glue before joining them. Put a weight on it to keep it together, then leave it overnight.
The world of Adhesives and Glues is really fascinating, all of my life I have built a myriad of mechanical /electrical prototypes and production devices that need to work in extreme conditions of temperature and mechanical stress and or corrosive atmospheres and finding the right adhesives makes or breaks a product.
I must say that the interior of a car is really difficult to achieve stable gluing due to the extremes of temperatures that dashes experience and also the unknown vapours that some plastics emit when heated. Let us know how you get on.
I like Richard choices for this and would be trying them first.
If you know what you're bonding and it's new, there aren't really too many problems. What gets complicated is the car restorer who for example, wants to bond new leather to old heat damaged plastic, when re-trimming his dash top. Assuming the dash top is PVC, but not really knowing, and not knowing how much heat damage it has been subjected to, makes it very difficult to bond. Forty year old plastic of some description, of undeterminable quality?
If it's polypropylene, or another polyolefin, then you have different problems, but I'm fairly certain the dash tray on a P6 is PVC.