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Why did the factory spray two coats of primer?
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westwoodblue
Posted 2018-09-06 6:29 PM (#569715)
Subject: Why did the factory spray two coats of primer?


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Any one of these cars I have bodyworked, there are always two coats of primer-

The base coating is the red-oxide everyone used back then, which makes sense. But over top of that, there is another coat.
Some have been white, others grey. It's obviously a primer, but why? It's not like the factory sprayed another coat to block
out, the only thing that would have made sense was another coat closer to the enamel color to save on paint. But this additional
layer never seems to be very close to the topcoat.
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uncltank
Posted 2018-09-06 10:47 PM (#569731 - in reply to #569715)
Subject: Re: Why did the factory spray two coats of primer?


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So that's where my primer went! My '57 Dodge didn't get primer on the floors underside or interior.
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miquelonbrad
Posted 2018-09-12 9:02 PM (#570029 - in reply to #569715)
Subject: Re: Why did the factory spray two coats of primer?



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My '57 Chrysler 2 dr got two coats of paint, and the paint code is restamped on the tag from the factory. Either someone screwed up, or an order came in for an identically equipped car, minus the paint choice... only the body has the two coats; all other panels and peices have the correct single coat.
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57chizler
Posted 2018-09-15 11:36 AM (#570143 - in reply to #569715)
Subject: RE: Why did the factory spray two coats of primer?



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westwoodblue - 2018-09-06 3:29 PM

Any one of these cars I have bodyworked, there are always two coats of primer-

The base coating is the red-oxide everyone used back then


Or, could that red oxide be the dip? Did they dip the bodies back then?
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57plymouth
Posted 2018-09-18 4:31 PM (#570322 - in reply to #569715)
Subject: Re: Why did the factory spray two coats of primer?



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Possibly a lighter top coat of primer for a light color paint. The red oxide was there to be the main adhesion base for the top coats. Similar to etching primer over bare steel now.
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1960fury
Posted 2018-09-18 5:13 PM (#570329 - in reply to #570143)
Subject: RE: Why did the factory spray two coats of primer?



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57chizler - 2018-09-15 11:36 AM

westwoodblue - 2018-09-06 3:29 PM

Any one of these cars I have bodyworked, there are always two coats of primer-

The base coating is the red-oxide everyone used back then


Or, could that red oxide be the dip? Did they dip the bodies back then?


In 1960+, they did. It was backed on too. Good stuff, it is like galvanized. I cringe each time I see someone sanding a good body down to bare steel.
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Chrycoman
Posted 2018-09-23 7:45 AM (#570607 - in reply to #570329)
Subject: RE: Why did the factory spray two coats of primer?



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Starting in 1960 (unibody cars) wemt through a series or dips and sprays :

Sprays - External
1. Alkaline cleansing (170-180 F)
2. 1st water rinse (150-160 F)
3. 2nd water rinse (140-150 F)
4. Phosphate coating (125-135 F)
5. Cold water rinse
6. Conditioner Rinse (140-150 F)

Immersion - Internal and External
The above six sprays were also done as immersion baths. For example, Alkaline external spray cleaning was done at the same time the body did an immersion alkaline cleansing dip.

Once the six immersion and spray steps were done, the immersion process did step #7 -
7. Rust preventative primer coating

Then came seven external finishing operations :
1. 1st coat of epoxy primer
2. 2nd coat of epoxy primer
3. Oven bake - 350-370 F
4. Wet sanding
5. 1st coat of enamel (Lustre Bond enamel at that time)
6. 2nd coat of enamel (Lustre Bond enamel at that time)
7. Oven bake - 250 F

Primer was noted for being porous which is why car bodies that were shipped without the final colour coats received a coat of white paint (bodies shipped in white). This was common with cars shipped CKD (Completely Knocked Down). The bodies would receive the colour coat at the plant the units were shipped to. CKD - Think full-size Revell or AMT kits but with the engines and transmissions assembled. And using welds instead of plastic glue.

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56D500boy
Posted 2018-09-23 12:44 PM (#570621 - in reply to #570607)
Subject: RE: Why did the factory spray two coats of primer?



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Chrycoman - 2018-09-23 7:45 AM
Primer was noted for being porous which is why car bodies that were shipped without the final colour coats received a coat of white paint (bodies shipped in white). This was common with cars shipped CKD (Completely Knocked Down). The bodies would receive the colour coat at the plant the units were shipped to. CKD - Think full-size Revell or AMT kits but with the engines and transmissions assembled. And using welds instead of plastic glue.


Bill: What was the situation in 1956 regarding Detroit and LA? Did LA start their production from sheet metal or did they receive stampings or partially assembled cars from Detroit? The reason I ask is I have seen some white as I have been sanding down some areas in advance of new paint. Maybe what I am seeing is primer. I don't know.

Just curious.

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westwoodblue
Posted 2018-09-24 1:31 AM (#570658 - in reply to #569715)
Subject: RE: Why did the factory spray two coats of primer?


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uncltank: Must have been! one of them is a 57, so it does add up

miquelonbrad: I expected something similar to this, if the car would have had a data plate, but there isn't one. I've tried rubbing compound on it like paint, and the
white underneath will polish as if it were paint. Only difference is the whole car (fenders and all) is white, like they made a mistake and went back to correct it. Or, it also occurred it might have been ordered white and two-toned at the dealer.

57chizler: I'm not sure, the car is a 57, did they dip any 57s at all? By the rust it didn't help any

57plymouth: Makes sense, too. One of the cars is the meadow green/white two-tone. When chemical stripping, the order goes (from substrate to top layer): red oxide, white primer/sealer, and on the green portions, it goes from the white primer/sealer to the meadow green (resprays and touch ups on top of that). On the white two-tone sections, there is a white sprayed on top of the primer/sealer. It's a real close match, which makes me think factory done.

1960fury: The primer they used definitely has stick to it. Chemical strippers won't touch it. It has stuck this well for so long, I can't justify removing it in places that don't need it. Seems like a lacquer because only lacquer thinner/acetone will remove it

Chrycoman: Never dreamed they did any prepwork on these in the factory (sanding, etc). "bodies that were shipped without the final colour coats received a coat of white paint (bodies shipped in white)." sounds like what I'm seeing. Was it done in earlier models as 56D500boy asked?

On another note, underneath the car is sprayed with a maroon metallic. It has to be original (On what was left of the floors, underneath the undercoating), there's no primer/coatings below it. I assume it's MMM "Burgundy Poly" on the 57 color chips chart. They sprayed some inside, too, from what I can tell. It's not in the trunk interior. I've got to hand it, if some forum member owned this heap, kudos on filling everything with spray foam and gluing the back glass in with silicone.

Edited by westwoodblue 2018-09-24 6:07 AM
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Stroller
Posted 2018-10-20 10:22 AM (#572034 - in reply to #569715)
Subject: Re: Why did the factory spray two coats of primer?


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I like to think they did things different simply because they were using virgin steel unlike today. I have seen plent of vidoes showing cars being dunked in colorant but I can almost gaurantee none of my cars every were, but at least they did get a primer spray. I had my Lil Red verified through the Chrysler Historial Society and I know where it was built. What is strange it has a paint run on the back of cab right behind the drivers under the rear window. It also has a bolt cross threaded right above the right rear tail light that does nothing and lastly the dome light lense has never had a light behind it becuase there is no socket to put a bulb in. But yeah painting back then was still better than today I like to think. After all you can take a 70 year old and buff it out and it will try to shine.
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