This gives me a deeper appreciation for cars with plastic body panels. I also wonder if DeLorean Motor Company took any of this into account when they designed the DMC-12 with stainless steel body panels.
And yes, that's a big reason why they went with stainless. Stainless steel does corrode, just much less visibly than regular steel. It also has different physical properties like work hardening etc. It's also VERY expensive. Salty napkin math says $10,000 more for the Cybertruck.
I was thinking about "molded-in color" panels like the old Pontiac Fiero. That makes sense, though, re: painted plastic panels. They'd be a whole different ballgame and there's, I'm sure, interaction between the paint chemistry and the plastic chemistry that's probably pretty hairy.
I bought 2 pairs of the same shorts a couple years ago, one in blue and one in olive. Both were used almost interchangeably in terms of exposure to sun, dirt, washing, and salt water. But on the green ones a section of the waistband is clearly differently colored where on the blue the colors still match.
Droplets were enough to cause problems - there's no hiding problems on a car's paint job and customers are VERY demanding.
I toured an assembly line a few years ago. The guide told us that in the 1970s they had teams of people watching iron/steel prices, when they thought the prices where at the low they made a massive order of all iron that factory would need for the next few years. When the factory when to just-in-time (sometime in the 1980s or 1990s) they couldn't do that anymore - but they also got to get rid of all the equipment to de-rust all that stored iron: since every raw material was shipped out as a final assembly in a week there was no time for significant rust to form and so they avoided a lot of problems.
You can still get squeezed so either way. But that has close to nothing to do with JIT, JIT just concerns the delivery bit (over simplified of course).
I was wondering how realistic that really is to DIY or if I’m kidding myself. Sound like even if I rented a stall in a paint shop for a few weeks, I won’t have the time to finesse the technique to get a good end product, especially with how much more finicky I understand the chameleon paint to be.
I don’t care so much about getting the matching perfect - “it was my first time” is a perfectly cromulent excuse in my social circles - but I do want the paint job to be good enough so that I’m not redoing it every year or two (I hate sanding). What should I exepct?
Only advise I can give is to get some cheap paint and some kind of panels and start practicing.
There's a limit on the number of tries you have to "repair" the paint job, because the vehicle has to go through the oven again to bake the coatings. The trips through the oven affect more than just the paint. Some panels are filled with foam; there's internal sealant and glue, and external sealant. All of those things don't really love being baked too long. For the shop I worked in, we got 2 tries to repair.
The main limit on repairs though? The windshield. Windshields are glued in with specialized urethane 'caulking'. They have to stick to the paint, and the paint has to stick to the body. That is only certified reliable with less than 5 trips through the ovens (in my shop).
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Paint is the hardest thing to get right in the whole assembly process, because there are so many process variables. Temperature and humidity (dew point) are the biggest besides the actual paint mix, but there's also unexpected problems from every direction. Our solvent paint process (pre-2013) was very vulnerable to siloxane (silicone) lubricants. Someone in IT applied some lubricant to a label printer and ruined hundreds of paint jobs. Livestrong bracelets also ruined at least a hundred paint jobs. Someone did weekend work on the roof? Congratulations on your dust quality spill (spill means a bunch of problems).
All of the parts of the paint have to work together, and that includes things that you don't think are paint. The body is just dumb metal, right? Of course not. The metal panels have oil on them in stamping, and they MUST stay oiled right up to the point where the body takes it's first bath. If too much of the oil has evaporated, then you start getting corrosion, and in many cases you won't be able to tell until the vehicle gets to the customer.
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Paint shops have the most complicating routing of any part of automotive assembly. The electronic quality and build data has to be synchronized with the physical process, and that data package can be updated by several different systems. Then either IT or OT (operational technology) can make a routing decision, or an individual can use a key switch to manually change routing. "Why did this vehicle go here" is not a straightforward question to answer sometimes.