I'm thinking about painting the plain aluminium sheet sides of my trailer (with a roller), anyone know what kind of paint/primer I should use, and if it needs any preperation?
I've used a two-part etch primer on aluminium, one part is phosphoric acid which you mix with the paint to get the required consistency for your method of application.
Got mine from here, I think these guys actually make it:
I've seen some of these etch primers and they seem to coat thinly - should they be flatted to provide a key, or should the next coats be sprayed before it is totally dry so it will bond to it?
spray etch,one wet coat,dont worry if it's a bit see through.let it dry.do not rub it at all.then your regular primer,how many coat of that is up to you.
it's acid base that bites into the metal/grp.and it is ready to take primers. rough/porous surface.
but i do rub over alli first,to give it a bit more key.
degrease ali too,even if new it is put through rollers that are oiled.when making sheets.so can get impregnated.
quick paint lesson
the etch primer doesnt need to be keyed as long as you put the normal primer over it after its flashed off,wait say 10-15 mins then put the normal primer on,also its not a case of anything needing to be rough for paint to stick to it,it just needs to be keyed,if the bare metal/old paint is ok an not scratched up etc a scotch pad will do the job just fine,red scotch for primer grey scotch if your going to prep old paint then paint straight over with new paint.
normal primer unless you use a wet on wet process will need to be flatted to make it smooth an key it up,u can use anything from 600-1200 for this.
but regardless of all that theres no point in using a normal primer and flatting it if your just gonna roll the panels,clean the panels scotch them degrease them,etch prime them to seal and protect the bare metal then just roll straight over them with the colour,this will be absolutly fine