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I'm going to go with the short version of this. Not because anyone wouldn't understand, everyone will. But because it's painfully boring. There are a couple people that need an answer though and it may help them in looking.
Everyone knows the fast rust through problem started in the 70's. With the intense competition from foreign imports the Big 3, not just GM, made a wholesale shift to using recycled steel for their sheet metal. That was the first domino.
The vast majority of sheet metal in a car is HRP&O. Hot rolled, pickled and oiled. Molten steel flows from a smelter and starts to cool when it contacts the air. It runs through a series of rollers that press it into the spec'd thickness. It's treated in an electrolytic acid bath, pickling, then through a hot air dryer, then oiled. The P&O part is supposed to stop oxidation in the un-painted steel. It usually works. But it has to be stored in a controlled environment. That's the problem.
Next, there's the manufacturing process at the stamping plant. A GM stamping plant orders steel by the train load. The largest coils I saw myself were 60"w x 120"o.d. Roughly 5-7 tons depending on the i.d.
I know they run larger coils, I just never saw any.
According to the Big 3"'s own QS9000 requirement for outside vendors, each coil is to be inspected as it's unloaded, and as it unrolls running into the blank press. They require that from vendors, but have exempted themselves from it. They use SPC instead. They generally check the stock once\hour and random stamped peices.
The blank is the unformed, cut to size peice that makes the component.For doors, fenders, hood and trunk lid, roof sections and floor pans, the edges are rolled over and more or less crushed. Roll forming. It eliminates the rough edge. But that's exactly where 99+% of auto rust through starts. When you roll the edges using recycled sometimes it's exactly in a rust spot in the steel. It's supposed to be caught by QC but sometimes it isn't. Because they use SPC. Random checks. The problem is in using recycled material. As steel ages it loses it's maleability. As you crush the edges it cracks. If you're using rusty, crap metal to start with what do you think the edges of the cracks are full of ?
In the old days this would be caught at the press or by the person running the spot-welder. But the auto co's went to robotic welders and eliminated the human. The original prototype robots ran in an extremely controlled environment that doesn't exist in a stamping plant. They shouldn't be there, but they're cheaper than paying a person. (This is where I could start my UAW argument, but I'm done with that) That was the second domino.
The last part of this is the use of robotics to paint. Since they've also eliminated the operator who used to catch this crap here, ther's no one to find this rust before the paint is already dry. Most of it is hidden by the coating, most that isn't is missed by the random SPC checks, a few parts are flagged and canned and the rest are sent on their merry way to the public.
That's the really aggrivating part from my view point. All of this was the result of cost cutting by the manufacturers. They had choices to make when Honda and VW first started this war. 1) Compete and accept a lower profit. You can hurt yourself laughing at that one.
2) Compete by using inferior material, demand benefit cuts by the workers, use the saved money to rigorously defend against complaints by the consumer, and still make big bucks.
I think I know which one they chose.
Bob
 

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Interesting post,Bob.I got into gm's paint problem a little further down the line from you,as in at the dealer.I have worked on the" peelers "for a few years back.We were told that they cut one of the primer processes which I'm sure was bull ca ca,looked more like they allowed too much time for the elpo primer to dry and the paint wouldnt lock up with the primer.We finished peeling them with a razor blade and did not even disturb the elpo primer.It was way too hard and slick to have held any kind of paint for a long period of time.G M really needs to get their act together on finishes.....just my 2 cents worth
 

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smc51 said:
Interesting post,Bob.I got into gm's paint problem a little further down the line from you,as in at the dealer.I have worked on the" peelers "for a few years back.We were told that they cut one of the primer processes which I'm sure was bull ca ca,looked more like they allowed too much time for the elpo primer to dry and the paint wouldnt lock up with the primer.We finished peeling them with a razor blade and did not even disturb the elpo primer.It was way too hard and slick to have held any kind of paint for a long period of time.G M really needs to get their act together on finishes.....just my 2 cents worth
I'm glad you read it and responded. And I was interested in your experience as well. Doesn't surprise me much. GM has had finish problems for a while. It seems to be a matter of consistency. I should say that I have nothing against GM. Of the approx. 3 dozen cars I've owned, probably 30 have been GM. But I ended up working for them, so their process is the one I know first hand. Though I know it's representative of the Big Three at the least.
I wrote that because a member here is having a door rust through problem with a 3 year old STS and getting nothing from GM but screwed. It was to tell him Why his car is rusty. Nothing more.
Unfortunately, I don't hide what side of the labor\management fence I'm on, so I don't post much anymore except car repair kinds of things.
Anyway, thanks for taking the time to respond.
Bob
 

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One thing about this whole deal is ,it just wasnt GM,they all,(the big three) had similar expirences,do not know much of the history on their probs but suspect a cost cutting deal simular to gm's.....hhhmmmm....another post perhaps........
 
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