Simple question - I'm making a cover out of ali for my boot space (actually, 2 end covers and a lid). I intend to form the ali found the curves and I'm bound to end up with little dents, etc.

I'm not too worried about this as I intend to paint the pieces anyway, so I'll fill and sand the surface just like any other bit of painted bodywork.

What I need to know is whether I should etch-prime the surface before using the Isopon, or will the stuff stick well enough without it? I'll be using etch primer anyway, once the surface is ready for painting, but I'm unsure of the sequence.

Cheers in advance,
David

i know nothing about ali but would it need filling,
as its so soft cant you just knock it back and file the surface or block it.

I think you'd have to fill - even the best metalworkers can't get a perfect finish on sheet ali without filing (as opposed to filling!) and sanding.

As I'm painting I'm not that fussed. Trouble is, paint will show every last defect, especially the semi-matt black I'm planning, so I expect that I'll have to fill.

DJ

Hi David I'm no expert but I think you have to etch prime the alli first then put a coat of primer then fill. When you rub the filler down you must not break through the etch primer if you do you have to re etch that area. The reason for this method is so that the primer and the filler will stick to the aluminium.
regards

Trev

Use plastic padding elastic straight onto well keyed ally (etch only provides a fine key you can paint over). You need the elastic as it will not crack as the ally moves

Thanks Mark (I was hoping you'd read this thread! )

David
(Oh - and thanks to everyone else, of course...)

I suggest wet sanding with 600 grit or so, then etching with a metal cleaner (with etch)-->>etch primer-->>base coat-->>clear. If you touch the ali sheet with your bare hands between the metal cleaner and etch primer, you'll have to clean the ali again. I did this once and the primer did not stick where I touched it. After this happened, I wore rubber gloves and never had a problem again.

--HTH, Chris

Fillers available in the UK are designed to be worked dry, if you use water, the filler will retain moisture and you will get microblistering.