I have also noticed? a lot of steel now seems to rust faster/sooner/easier then used to, is there a difference in the steels or is it the air having more stuff/contaminates in it. Thinner car body metal does not help.
I think you are right. The fact is that cars are about the most recycled product there ever was. Scrap steel makes the steel both better and worse. The process of rolling thinner sheet metal doesnt help.
I don't think the air quality has any major affect on the results. But road salt and air humidity certainly does.
I agree with earlier comments on the heavy undercoating. I think the waxy oils are better.
Over the last two years,
@Dabbler and I have collaborated on some testing of a variety of anti-corrosion products on some farm equipment. Like so many other projects, interest fades rapidly once the problems are solved. So we didn't finish or publish a report.
What I can say is that the degree of rust protection provided by various products is remarkable. After a lot of discussion, we decided to test the following products on my furrow plow blades after plowing brings the blades to highly polished bare steel.
Old engine oil
Grease
WD40 Corrosion Inhibitor
Fluid Film
Liquid Wrench Corrosion
TriFlow rust preventor
Rust Check
Krown rust protection
Keeping in mind that this was just one set of anecdotal tests using products that were all very casually applied, the summary recommendations are as follows:
Long term outdoors exposure - use Fluid Film sprayed or brushed on liberally once a year. The level of protection and low cost make the difficulty of removal worth the effort.
Long term Indoor exposure - use WD-40 Corrosion Inhibitor once a year. It is expensive but is more easily wiped off, provides superior corrosion protection, and also adds good lubrication. If cost is a factor, use Fluid Film but be prepared for some cleanup effort when you want to use the tools.
Here are the cost factors from back then. I'm sure they have changed since then:
Fluid Film is $20 in a 1/3 Litre Spray Can (what I used) @Crappy Tire. A 3.7L pail is $120. Amazon has the same price for the spray cans, but the Pail is only $82.
The WD-40 Corrosion Specialist is $32 for a 6.5oz (1/5 Litre) spray can. (About double the cost of Fluid Film per unit volume in small quantities.) as far as I know, it isn't available in pails.
I recently noticed that Fluid Film has a "Black" protective film now. Another experiment for next year.
Last but not least, here is an extensive thread well worth reading for anyone with rust problems 'Rust is the Enemy':
Humidity is a constant challenge living here in SW Ontario. Humidity breeds rust like an invasive species.
I saw a thread just now by
@Johnwa about this VERY COOL Collet Box he made. I am SOOOOO jealous! Not just because the box is REALLY COOL, but also because I'd be terrified of putting my collects into an enclosed container of any kind in the hot humid climate I have here in SW Ontario.
https://canadianhobbymetalworkers.com/threads/collet-box.3590/unread
I've tried to handle humidity and rust in numerous ways by:
1. Keeping tools and bits well oiled. Spray oil is awesome...