Jayson m wrote:Then how do you paint new oem sheet metal with e-coat primer or brand new bumper covers?sanding them and applying proper shade primer then sanding them again before paint is counter productive.sealer is an important part of the repair process imo and not a waste of time and money.I don't know what it's like in your country but sealer has many benefits in a Collision shop here.

I've discussed this with DuPont/Axalta on a number of occasions. They're quite happy with us cleaning an scuffing electrocoat panels then straight to a valueshade primer, sand then base and clear. That's good enough for lifetime warranty support from them.

Probably more than half the bars we get are already primed, so scuff and paint only for those. Some of the European bars come with specific no sanding instructions - just clean with an alcohol, not solvent, cleaner and paint. Where bars are unpainted we use 901R/907R which is a special plastic primer that is designed for wet-on-wet. So, no sanding at all - the item stays in the booth until complete.

Full resprays and restorations are different - there we do use an epoxy over the bare metal, but basecoat goes over primer, not an intermediate sealer. We also use sealer where there may be a compatibility issue or repairs on panels that have been repaired before where the exposed feathered edges present a risk of frying up, but, again the sealer goes under the primer, not over it.

My point in all this is that primer is designed as the perfect substrate for basecoat and should not need a sealer over it. Does sealer provide a better bond between the base and a primer, or a better bond even just to the basecoat? Debatable, but not in my opinion, although I should point out that we use solvent base and the solvent does melt into the primer, just a little, but enough that, when combined with a properly sanded (P600-P800) surface, we have never had an issue of adhesion. For waterbase the situation is obviously very different.

So, I'm not saying that the use of sealers is wrong - just that we haven't ever found them necessary and the additional cost in both materials and time I can't see as warranted.

Interesting,what your reps say is completely different than what ours say in north america. Base coating over a primed factory bumper is a no no and no warranty will be provided as it needs to be sealed.Im not saying your wrong as I agree with perfect prep on a 2k primer going to base coat is OK.My question was how you handled new oem parts without sealer. So I still say sanding an oem ecoated part,then applying your primer,sanding it again,then painting is not efficient.You can cut your time in half by applying sealer and paint wet on wet.It is not an approved procedure to base over a primed bumper or a raw plastic cover with adhesion promoter without sealer.I have never heard of solvent basecoat "melting " into a 2k urethane primer,it is a mechanical adhesion due to the scratch you put into it. We agree to disagree but still interesting to hear how it's done else where.

I would have to lean towards Jayson on this issue. Sealer only goes over primer or sanded ecoat. I dont use sealer very often because I use a DTM primer that is suitable to paint directly over. I do use a ground coat if the paint code calls for it. But I just do the basecoat ground coat and not the sealer version. Basically in my shop sealer only goes on new parts that are ecoated then sanded with 600 grit. Or bumpers come primed I just scuff with a scotbrite and spray sealer. Or if they are bare plastic I scuff spray adhesion promoter then sealer. On real cheap jobs I will sometimes just paint directly over the adhesion promoter.