Sticking wooden quad to powder coated aluminium?

Hi everyone,

We have a large pivoting front door, the surround is all black powder coated aluminium, and the walls are rendered brick. There is a gap of between 3mm to 8mm between the door surround and the rendered wall and I would like to stick a piece of black painted quad there to seal up the gap. I've tried using silicon but that didn't do a very good job at all and pretty much fell off after a couple of days. Does anyone have any suggestions for an adhesive that would bond the quad to the powder coated aluminium?

Thanks!