Modern car paint and rust

I thought that at some point, they started requiring galvanized body panels.

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Am Sonntag, 12. Februar 2017 20:02:27 UTC+1 schrieb Ignoramus20243:

This is also true, I think. But I don't see the modern paint cracking and falling off, so I'm wondering what's better about the paint.

Don't think there's any "requirement" other than what the manufacturer thinks suits their purpose best as far as whether panels are/aren't galvanized (or otherwise treated). I don't know what actually is most common other than there's a tremendous fraction not that isn't even metal; just pretty sure there's no mandate re: same. The mandates are those for the fuel mileage averages so that means "lighter is better" in ounces quantities.

As for paint, what has improved is they've finally figured out formulas that have at least some longevity after the EPA restrictions on VOC's killed all the traditional finishes as not being within those limits.

Big thing was change to the surface preparation of the steel to either electrostatic wet application or full body dip of a high quality etching primer which I believe contains Zinc. This was combined with the use of high strength steels and "galvanized" steel in rust prone areas.

the 1990s, this changed - and quite suddenly. Does anyone know what specif ic changes were made to the paint composition and surface treatment? I can only find vague allusions in most articles.

Right. It's better coatings, better primers and protection, and better appl ication. Read, water-based coatings that often are based on urethanes; phos phate and weldable, etching primers; galvanizing in rust-prone areas; and e lectrophoresis and electrostatic application. The first water-based coating s -- used into the '80s by some manufacturers -- had poor adhesion and didn 't weather well. They're MUCH better now.

All of this became more necessary as body panels got thinner, with the use of AHSS (advanced high-strength steels; a continuing evolution of the HSLA [high-strength, low-alloy] steels that were first used in the '70s). Rust i s potentially a bigger problem than ever because the steel is thinner.

Am Sonntag, 12. Februar 2017 23:03:10 UTC+1 schrieb snipped-for-privacy@gmail.com:

plication. Read, water-based coatings that often are based on urethanes; ph osphate and weldable, etching primers; galvanizing in rust-prone areas; and electrophoresis and electrostatic application. The first water-based coati ngs -- used into the '80s by some manufacturers -- had poor adhesion and di dn't weather well. They're MUCH better now.

e of AHSS (advanced high-strength steels; a continuing evolution of the HSL A [high-strength, low-alloy] steels that were first used in the '70s). Rust is potentially a bigger problem than ever because the steel is thinner.

Are these modern coatings two-pack paints? Or some kind of stove enamel whi ch is baked on? I also remember hearing something about paints which contai ned cyanide at some point.

I'd be interested to know the composition, because they seem way better tha n anything I can buy.

Thanks for the replies!

Chris

application. Read, water-based coatings that often are based on urethanes; phosphate and weldable, etching primers; galvanizing in rust-prone areas; a nd electrophoresis and electrostatic application. The first water-based coa tings -- used into the '80s by some manufacturers -- had poor adhesion and didn't weather well. They're MUCH better now.

use of AHSS (advanced high-strength steels; a continuing evolution of the H SLA [high-strength, low-alloy] steels that were first used in the '70s). Ru st is potentially a bigger problem than ever because the steel is thinner.

hich is baked on? I also remember hearing something about paints which cont ained cyanide at some point.

han anything I can buy.

I wish I could give you a simple answer, but the chemistry of automobile pa ints has exploded in many directions over the past ten years or so, and the chemistry is mostly over my head.

Around the world, each manufacturer seems to use something different. There are water-born systems and solvent-born systems; two-wet and three-wet sys tems; integrated primers and self-sealing clear coats (Nissan). It's wild o ut there.

Some of the primers and clear coats are catalyzed before application. I *th ink* the base coats are not. Some are described as melamine-based; others a re described as acrylic, urethane, or polyester. Water-based systems seem t o make up the majority. Again, the chemistry is beyond me.

Before I retired I was working on an in-depth study of Ford's production, b ut I didn't get very far. They have a new two-wet system with no clear coat ("monocoat") and it may be the leading edge. I suspect it's from Axalta.

If you want to talk to someone who specializes in this stuff, I may be able to get you some names.

At some point in the last 2-3 decades, I recall seeing a commercial on TV where the US mfgr touted that both vehicle frames and body panels being dipped in a rust-proofing hot bath of some sort. I quit TV 13 years ago, so it was well before that.

The painter at work sprayed my old '72 Int'l Scout with Imron, a

2-part aviation paint. It was over $100/gal way back then ('82, $3-500 now), but a friend had given it to me, the spare from painting his '48 Willys wagon. Tony was the kind of painter who was somehow connected with the paint and he could colormatch and stand up the metalflake replacement paint like the original, so you couldn't tell the difference. A true _artist_.

Have you talked with painters or automotive paint supply shops there across the pond, Chris? They're fonts of knowledge, if you can get them to spare you a few minutes.

Why the change to base plus clear coat? I took an auto body class in high school, we had lacquer and enamel,

44 years ago. The hood on my sons Toyota had faded and was blotchy. So I went to the paint store to buy paint. I thought I wanted lacquer, I was quickly educated that I wanted a base and a clear coat. It turned out good especially for an outdoor job. We did end up with a small hazy area, when we started the motor to move it in the garage, before the dew came. Just one area on the right side near the windshield. I suspect it would buff out, but he took the car back to college, so haven't tried. Mikek

in the 1990s, this changed - and quite suddenly. Does anyone know what spe cific changes were made to the paint composition and surface treatment? I c an only find vague allusions in most articles.

application. Read, water-based coatings that often are based on urethanes; phosphate and weldable, etching primers; galvanizing in rust-prone areas; a nd electrophoresis and electrostatic application. The first water-based coa tings -- used into the '80s by some manufacturers -- had poor adhesion and didn't weather well. They're MUCH better now.

use of AHSS (advanced high-strength steels; a continuing evolution of the H SLA [high-strength, low-alloy] steels that were first used in the '70s). Ru st is potentially a bigger problem than ever because the steel is thinner.

Clear coats retain their gloss much longer than standard base coats -- up t o eight years for some current ones -- and they contain IR blockers that ex tend the color life of base coats. They've been standard for years.

That is, for the common "three-wet" (primer, base, clear coat) systems used by most OEMs. As I mentioned earlier, Ford, among others, has gone to a "t wo-wet" system for commercial vehicles and probably will go that way for ca rs. The current two-wet system used by Ford supposedly maintains gloss for eight years without a clear coat, but it only works in light colors for now .

These are chemically so far removed from our experience with lacquers and e namels that it takes an expert to explain them accurately.

Am Dienstag, 14. Februar 2017 03:43:47 UTC+1 schrieb snipped-for-privacy@gmail.com:

le to get you some names.

Thanks, Ed. That's a kind offer. Here's the question in a different form. I 'm working on a book and I want to know how to get a coating with a similar performance (modern car paint is, as far as I can see, way better than any thing I can get in the shop). It doesn't have be a unique or comprehensive answer, but it needs to be a practical and understandable method. Any idea of someone who could help?

Best wishes,

Chris

Am Dienstag, 14. Februar 2017 14:52:42 UTC+1 schrieb Larry Jaques:

Good idea. I don't know of a specialist shop in the area, but I can look for one.

A number of years back, I had my '90 lumina van in to the dealers for some type of service and the service advisor recomended that I visit thier body shop about the clear coat failure on the (black) area above the front seating section. They gave me a "quote" of $750.00 reduced by 50% to $350.00 to return it to "as new". A few months latter, he practicaly begged me toget it fixed for free. I presume thet it didn't look good for GM's reputation.

Ed, if I buy a modern car like a Honda, how long can I realistically expect them to last?

You got any repo lots around where they sell stuff? I've got a big one not too far away and it's very educational to look through. All sorts of models, years and condition with no cleanup, prepping done for resale.

I spend most of my time looking underneath the vehicles. The front wheel well on the Honda CRV is quite interesting. Doesn't look like a very long lived design for this area and road salt.

Another one that caught my eye was a Buick Rendezvous. The gas filler is located above the rear wheel well. The filler pipe is in the well with a thin protective material over some of it.

The Chevy Colorado that has all the emergency brake cable connections inline with where the left front tire will throw all the road spray on them.

The 2007 Chevy Silverado that had rear frame rails with major crusty rust trouble.

Most people look at the body color/paint, interior... I get down and look all around underneath. The exhaust, drive shaft, suspension, wheel wells, emergency brake cables, frame rails :)

On 02/16/2017 8:06 AM, Leon Fisk wrote: ...

Years and years ago (before 1978 as hadn't made the TN from VA move yet) used to travel to Cleveland and Wickliffe, OH, regularly for employer as had a major subsidiary/vendor there. Once coming back to catch the corporate flight back to Lynchburg that evening, an old rust-bucket pickup literally did hit a serious pothole in the pavement and the frame buckled behind the cab to the pavement. Created quite a backup pretty quickly; fortunately I was able to get past and on to make the flight but was educational!

I remember also that all the freeways were just littered with mufflers and other body parts that had rusted to the point of falling off...not what we were used to in Lynchburg, VA, or even in KS where, while it's cold, it's so much drier don't have the rust issues.

A bit of an open ended question. I have a 97 Toyota T-100 that still looks beautiful and runs great. Will admit we had the sides of the bed repainted, not because of any problem but because we used as a work truck and the idiots that loaded it rubbed their belt buckles on the bed as they loaded it. They put a bunch of scratches in the paint. I'm in the Florida sun and after 20 years the roof and hood still look good, we do garage it though. Mikek

Yes.

They have a reputation in the rustbelt :)