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On Wednesday, February 22, 2017 at 3:37:42 PM UTC-5, Clare wrote:
On Tue, 21 Feb 2017 20:57:35 -0800 (PST),
wrote:

On Tuesday, February 21, 2017 at 11:49:35 PM UTC-5, Clare wrote:
On Tue, 21 Feb 2017 14:09:42 -0800 (PST),
wrote:

On Tuesday, February 21, 2017 at 4:44:19 PM UTC-5, Clare wrote:
On Tue, 21 Feb 2017 12:03:45 -0800 (PST),
wrote:

On Thursday, February 16, 2017 at 8:42:27 AM UTC-5,
Ignoramus20725 wrote:
On 2017-02-12,
wrote:

Right. It's better coatings, better primers and
protection, and
better application. Read, water-based coatings that often
are based
on urethanes; phosphate and weldable, etching primers;
galvanizing
in rust-prone areas; and electrophoresis and
electrostatic
application. The first water-based coatings -- 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 is potentially a bigger
problem than
ever because the steel is thinner.


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

Jeez, that's above my pay grade, Ig. There are just too many
variables. I can tell you, though, that eight years is more
or less the industry benchmark these days, and when you dig
into their technical literature, you'll find that ten years
is a frequent target for the latest treatments.
A lot of today's vehicles have a 10 year rust "perforation"
warranty.
If you get a bubble in the paint you KNOW there is perforation
allowing moisture in from the back.

Right. Those warranties generally are for perforation. The eight
and ten-year terms I was talking about are for gloss -- and they
aren't guarantees.

As I think I mentioned, the newer automotive paint systems are
looking for gloss, usually for the clear coat, but in some cases
for the base coat with no clear coat (like Ford's new system,
which they aren't using for cars yet).
Even Ford's "clear coat" in the early 2000s isn't really
"clear" - it
is a translucent colour coat (It's pealing a few spots on the '02
Taurus.

I'm keeping an eye on my 2004 Focus and my 2004 Sonata. So far,
they're both bright and shiny, with no rust (except under the hood
of the Focus, which has what looks like plain carbon steel
fasteners under the hood. Stupid, to save maybe 50 cents over
galvanized or stainless.)
Stainless never used under the hood - nor Galvanized We used to use
either electro-zinc or more commonlt cadmium plating - but it is
virtually impossible to do cadmium plating in North America today
with
EPA rules. The choice is plain steel American bolts or Chinese
Cadmium. What would YOUR choice be???

Most underhood fasteners I've seen are conversion coated with zinc or
some other phosphate. The bolts on my Hyundai have a black coating on
top of some kind of zinc. After 12 years it's gotten pretty fluffy and
looks like electrogalvanizing.

The Ford bolts look uncoated.

--
Ed Huntress

Despite New England winter road salt the hardware on my 91 Ford came
off easily and was still in good shape when I removed the bed, gas
tank and front-to-rear brake line last summer. LPS-3 long ago helped
but I couldn't reach everywhere underneath with it.
-jsw