Hi,
Yes you need to use an "etch" primer for the aluminium panels otherwise the paint won't "stick" Etch primer can be used on steel at the same time. I painted my MGA which has aluminium doors bonnet and boot skins with the stuff.
The temperature of the spray booth really depends on the paint you are going to use, most spray booths are of the "low bake" type which is to accelerate the paint drying times.
The crazing on the boot lid could be due to a number of factors, such as age, pollution, strong sunlight etc. The fender may of been painted more recently and with a different type of paint. It sounds like the clear coat laquer may be beginning to fail, is you car a metallic colour eg silver?
The best way of prepping the panels, especially if you are unsure of the current type of paint is to strip the car back to bare metal, this had problems associated with it, mainly that of time, you don't want to strip it, leave it for weeks and then get it painted! In addition the Aluminium panels are relatively "soft" compared to steel and thus are easily damaged by power tools, grit blasting,and some chemical paint strippers although brake fluid is good! Also the aluminium oxidises quite quickly if exposed to air which must be avoided otherwise the paint will not key very well.
An alternative is to "flat" off the panels and spray it with an isolator so that you do not have a reaction between different types of paint.
Finally the paint types available vary so much I can only speak from my experience.
Cellulose-
I have mainly used Cellulose in the past because it gives a finish in character with the age of the car, it's easy to spray without special equipment and will shine up very nicely. It's not a very hard paint and thus tends to age relatively quickly. Unfortunately it is getting difficult to obtain in the UK now due to EU laws.
Enamels-
these were an alternative to the above, mainly used on Lorries (trucks) and buses, it's quite tricky to use, but like cellulose doesn't need special equipment to spray. Much harder and you can get a good shine on it with alot of elbow grease! I use it on my stage rally car as it's cheap (ish) and readily available.
Ios-Cyanates (Two Pack)
Basically like epoxy glue, mix harder and base together and spray. extremely nasty stuff and you need special breathing equipment to use it, really a job for the proffessionals, all modern cars are painted with the stuff. Extremely hard wearing and keeps it's shine with little or no attention.
My only comment on it is that it can look wierd on a classic car unless the colour is chosen with great care, to me it seems just too shiny
I am afraid at the end of the day its all down to time (equals money). To spray a car takes about 20 minutes, however all the effort is in the preperation, the better it is done the better the final job
For example the BMW 2002Tii I painted from bare metal had
2 coats of etch primer with high zinc content for rust proofing
2 coats of high build cellulose primer
flat off with 800 grade wet and dry
2 coats of high build primer (different colour)
flat off with 800 grade wet and dry
2 coats of 70% paint 30% high grade thinners final colour
flat off with 1000 grade wet and dry
2 coats of 50% paint 50% high grade thinners
flat off with 1200 grade wet and dry
2 coats of 40% paint
Left to harden for two weeks and then buffed up
Took me about 10 days in my shed!
Ops went on abit sorry!
Malc
