TheMidnightNarwhal wrote:Honestly though I think the the basecoat and 2K clear is good, and like I said guys, I just want this to last maybe 3 years at most, so when it starts to let go I'll re-do it with good stuff.
I tend to agree. It's just the black around the window frames after all. You can do with basecoat and the 2K Spraymax clear and get a fairly decent job, limited mainly by the lack of pressure in the can which may lead to a bit of peel in the final result. On narrow trims you'll hardly see it.
Often those window trims are alloy or stainless which is then covered with a type of vinyl to black out according to the manufacturer's reading of the market and whether balck or bright will be better accepted. Sometimes that vinyl/plastic covering can be quite difficult to get off - be careful and patient if this is the case with your car.
chopolds wrote:Still lots of misconceptions here.
Understatement of the year.
Believe it or not, I started a reply to this thread yesterday and didn't finish. Saved it and here it is. Some things have since been addressed but I couldn't stand the thought of deleting it.
chopolds wrote:Chris, just so you know, acrylic lacquer and acrylic enamel are 2 totally different creatures here in the US.
As to answer the question. "Back in the day", there were 3 paints available to us (before urethanes came out, around 1982?). Enamel, or synthetic enamel, Dupont called theirs 'Dulux'. It was a slow drying, good glowing hardy paint once it finally dried. I've seen cars that were done with it actually still be soft after weeks.
This was eventually evolved into acrylic enamel, Dupont's Centari, for example. These were still enamel, but dried faster (still not "fast"), and more durable. There were even 'hardeners' you could use to make them cure, instead of dry, pretty quickly, and make them even more abrasion and chemical resistant. Later yet, they even make a "2 pack" hardening system that really made the paint nice to work with, and even nicer looking (more clear, more depth).
But these were still the work-a-day paints. For more glamour, you could choose lacquer. Very fast dry, thin, paints that you could easily sand and buff to get a mirror finish (even without clear). The high end custom and show cars often used these. Many more coats were needed for a good film thickness. Easier to use by hobbyists, as well. You could stop and sand out a bug or run after 15 minutes, and keep spraying. Fast enough dry to do outdoors, without worrying.
It's a strange industry, isn't it?
Dulux here is house paint, has been for longer than I can remember. However Dulux, which was owned by ICI, also were involved in automotive, using the "Duco" brand, which was licenced from Dupont and started as nitrocellulose, progressing later to acrylic. In Australia "duco" means car paint, e.g. "Don't damage my duco". They dropped the automotive range about the time of introduction of urethanes, maybe 30 years ago, and then about 10 years ago picked up the Nippon Paints automotive range which was marketed as Dulux Autocolour and included an acrylic, Autosolv. ICI sold the Dulux operations to PPG and then, in 2019, all shares in Dulux were bought out by Nippon Paints. They still market as Dulux in architectural, given that they have a market leading position and have a small presence in automotive.
From the 1960s the biggest name in automotive was PPG. Their product was called Dulon and was legendary for ease of use but by the early 2000s PPG's focus was on Deltron and their colour support for Dulon and Cobra/2K dropped through the floor. Although I'd been using Dulon for many years this lack of support prompted a change to Dupont for me, and many others. Dulon languished. Then PPG bought a small Australian paint company called Protec that was about to go under following a rash of delamination claims. PPG fixed the chemistry, moved the Dulon name to Protec and set about marketing the package as an economical, but still good quality, alternative to their premier brands. That they've now done quite successfully and colour support is much improved, but still lacking compared to Axalta.
Dupont have had L400 acrylic in their Cromax stable almost since the Dark Ages. In terms of use it's much the same as Dulon but colour support is much better. That said, in both brands the support is not as good as in the top of the range products. I still use L400, either as a standalone product or as a basecoat. Great product and very economical. It's this economy that has it as one of the favourites throughout Asia and that popularity means that Axalta have to continue to provide colour support, even if the North American and European divisions want to drop it completely.
A couple of other manufacturers also have acrylic, but they're a drop in the ocean compared to the two major players.
Enough of the history lesson. But it will serve to explain some references I make.
Acrylic enamel was around from the end of the nitrocellulose days, but, as you say, it had to be baked. For those refinishers who could afford one of those new fangled paint booths it was a big selling point, differentiating them from the average shop which was using acrylic lacquer which could be air dried. The lacquer won the marketplace race with enamels being largely relegated to spray cans for your garden furniture or bigger quantities for your tractor, a good example of a modern, fast drying formulation being Nason NI-640 (
TDS here or the 2K version Ful-Cryl
TDS here.
Here's a part of the TDS for Cromax L400 acrylic. It actually says 1K Enamel, but that's wrong. It's lacquer.
And here's the Dulon.
These days I don't think that enamels (acrylic or otherwise) even have a place in automotive applications. I only use a cheap air dry enamel for steel ute tray bodies for one car dealer customer and even then the booth remains sticky for days. Hate those jobs, but they're quick and they're profitable, so what do you do?
So, when I talk about acrylic I mean acrylic lacquer, basecoat (solids and metallics/pearls) and clears (not to be confused with our UK cousins who refer to any clear as "lacquer").
As you say, high end custom jobs were, and still are, done in acrylic. Why? Generally because it makes the paint job "period correct" for older cars but also because it (IMHO) actually looks better.
This is gorgeous, and acrylic. Not mine unfortunately but I'd love to do one of these.
Also as you acknowledge, acrylic is easier to use for hobbyists as well. More coats? Yes, but not as thick so the huge hangers that are common with urethane clears just weren't an issue. Yes, runs happened but they were easy to fix. Fully legal to use, in your garage, in Great Britain and lots of Europe, as well as Australia. Obviously much safer.
So why the change. Well, as I said, it was driven by the paint companies and the refinish industry which was being squeezed by insurance companies to the point where the time needed to cut and buff a repair job just wasn't being paid for. The prospect of urethane with an off the gun, out the door possibility was very, very attractive.
Have we been sold a pup? It's my suspicion that that is so. Done properly a urethane clearcoat over basecoat can certainly be very durable and I've never experienced any failures in jobs I've done. But.....I'm not the average shop where there's constant pressure to get jobs out the door and waiting for proper flash times isn't on the menu. Instead they wet-on-wet and a few years later the customers come to me and say "my paint is failing". Why?
First we have to understand that urethane clear bonds to base using a process generally called "cross-linking". In simplistic terms this is adhesion at a molecular level where atoms of the two parts cross link (a bit like a chain) to provide adhesion. However this bond does not go very deep and is highly susceptible to being broken by exposure to UV radiation. So, strict attention must be paid to ensuring that flash times are correctly observed and that clear is applied at the recommended thickness (because it's the clear that contains UV inhibitors to protect that bond).
Urethane clear is expensive. So it's in the interest of every factory manager to control clear coat use and put it on as thin as possible. Consider Toyota. 10 million cars/year and $10 saving on clear coat per car. That's $100 million improvement on the bottom line!
Reducing clear coat thickness has become an art form amongst manufacturers who openly admit that the paint that they apply has a 10 year "design life". Only problem is that life assumes average use, not "harsh" which includes being left out in the sun. So we're routinely seeing paint thicknesses of 70 µm ex factory. Now how's that going to work if the clear should be 60µm, the base 15-20µm, primer and e-coat at 5-15µm each? Well, it works by cutting down the clear coat thickness. Simple.
In the refinishing market the same drivers are leading to similar results. Painters, under pressure from the boss are cutting flash times and (quite often) only putting on a single coat of clear to keep costs down (and bonuses up). So now we have solvent entrapment adding to the weakening of the clear to base bond. No wonder it doesn't last. And why would they care? Warranty's long expired, it's no longer their problem.
Acrylic though, is a very different kettle of fish. A full acrylic system paint job involves acrylic primer, basecoat and clear. Although they look, and perform, different, chemically they're virtually identical. So when a coat is sprayed on top of another the solvents in it actually melt the top of the substrate coat creating a bond that is unbreakable. It's easy to peel fresh urethane clear off basecoat - absolutely impossible with acrylic. So, instead of a series of dissimilar layers, clutching to stay bonded to each other we have, in acrylic, a single film of layers which are "welded" to each other.
What does that mean? Well, for a start clearcoat delamination is virtually impossible and water cannot attack the base/clear bond by getting through the urethane (yes, urethane is not waterproof). Quality acrylic clears contain UV inhibitors to reduce fading of the basecoat underneath and performance, if applied at the correct thicknesses, is no worse than that of a base.clear urethane system. Properly cut and buffed an acrylic can look as good, if not better, than a urethane BC/CC system. Lots of show cars out there to prove that.
Repairs can be much easier with acrylic. Mid panel blends that are totally invisible were routine "back in the day". Bonding of new layers is much better.
Downsides? Certainly in production there is more labour required to cut and buff. But, in restoration and amateur that's a process that is normal, so no real disadvantage and acrylic, certainly when relatively new, is relatively soft and easy to buff. Acrylic is not as resistant to some solvents (notably petrol and acetone) as urethane. Acrylic does age, drying out and cracking after prolonged exposure to the sun. However, this exposure is generally much longer than that required to cause failure in most factory urethane finishes. Keeping the vehicle out of the direct sun and giving it a coat of good quality polymer polish can delay degradation significantly. For example. I did some work on a 1966 Holden a couple of years ago. The car had been kept under a carport, so not completely garaged and had had one panel refinished at some stage but all the rest was original factory. Buffed up almost like a brand new car!
TheMidnightNarwhal wrote:The clear coat SDS description says it is "Two-component acrylic resins and Activator: aliphatic isocyanates ". That still sounds like acrylic but just with a hardener rather than a urethane paint right?
Essentially, yes. There are 2 pack acrylics, acrylic urethanes and various types of other urethanes.
Base coats are not urethane. Generally acrylic or modified acrylic co-polymers.
chopolds wrote:Acrylic enamel will wrinkle up if modern urethane clear is applied over it. Well, sometimes.
Sometimes, but not usually in my experience. What will fry up is the exposed edge of a 2K primer that's been thinned out when feathering an edge or that horrible thermoplastic resin crap that the Koreans were using on bars and mirrors and GM used on door handles. In either case, enamel or thermoplastic, remove completely before refinishing.
JCCLARK wrote:Acrylic enamel can be used by itself all alone, it's a good quality paint that
holds up to the environment,
True. We used to paint repair areas with metallic acrylic, blend the edges and buff. Job done.
TheMidnightNarwhal wrote:I think from what I read acrylic enamels are still more durable.
Unlikely.