Finish on spindle support

[Gary B.]

Finish on spindle support

Joe,

Well, the newest edition of the '66 TIM&JG has things confused then. It says "The rear spindle support is a steel forging with casting numbers and dates ... and has a black finish ..."

So, the use of the word forging is incorrect, and who knows about the black finish. Maybe the TIM&JG revision team felt the previous painted description was incorrect and assumed a forging would appear black, similar to being painted. But if it wasn't forged in the first place, some of this logic doesn't make sense.

Gary

[Joe L.]

Re: Finish on spindle support

Joe,

Well, the newest edition of the '66 TIM&JG has things confused then. It says "The rear spindle support is a steel forging with casting numbers and dates ... and has a black finish ..."

So, the use of the word forging is incorrect, and who knows about the black finish. Maybe the TIM&JG revision team felt the previous painted description was incorrect and assumed a forging would appear black, similar to being painted. But if it wasn't forged in the first place, some of this logic doesn't make sense.

Gary

Gary------


I can absolutely guarantee you that these spindle supports were NOT forged pieces. Anyone that thinks they are does not understand the difference between a forged and cast piece. This includes ALL 1963 through 1982 spindle supports.

[Mark G.]

Re: Finish on spindle support

[Gary B.]

Re: Finish on spindle support

Mark,

When you say the spindle supports on your '66 are black, do you mean they are painted black or semi-gloss black?

Gary

[Gene M.]

Re: Finish on spindle support

I would bet the black finish originally was a phosphate or black dry film. It was a typical coating during that time period on castings for other industries.

A black oxide looks very thin and flat dull sheen but was not as cheap. Rust goes right thru it too.

[Joe L.]

Re: Finish on spindle support

Mark------


Thanks. This sort of information is the kind that's extremely interesting to me and I mean EXTREMELY.

For clarification, is the Chevrolet nodular iron foundry the one sort of "across town" from the gray iron foundry and later called something like "Casting Technology Center"?

When I was last in Saginaw about 20 years ago, this foundry was operating. However, there was another foundry that was located, basically, "across the road" from the gray iron foundry that was closed and looked like it was long closed even at that time. As I recall (I've got photos here somewhere) it was like a very large rectangular building with a "tear-drop" shaped water tower. It seems like someone told me it was a GM foundry that was only in operation for a short time. If I've asked you about this before, please forgive me.

[Gerard F.]

Re: Finish on spindle support

Joe,

I took a closer look at my spindle support and cleaned off some of the red rust and looked at a somewhat protected area.

Here's a photo of the machined eye area:



To me there is definitly some sort of black coating on the spindle support.

Whether it is paint I'm not sure. I tried grease remover, lacquer thinner and then paint-varnish remover on the eye. None of the black would rub off. Must be some type of chemical treatment or resistant coating or treatment.

If it were black rust, what would the makeup be?

Just having fun on a rainy day

[Joe L.]

Re: Finish on spindle support

Joe,

I took a closer look at my spindle support and cleaned off some of the red rust and looked at a somewhat protected area.

Here's a photo of the machined eye area:



To me there is definitly some sort of black coating on the spindle support.

Whether it is paint I'm not sure. I tried grease remover, lacquer thinner and then paint-varnish remover on the eye. None of the black would rub off. Must be some type of chemical treatment or resistant coating or treatment.

If it were black rust, what would the makeup be?

Just having fun on a rainy day

Jerry------


Iron oxide has many forms. These forms vary in coloration from dark red to black. The coloration on the spindle support ear appears to me to be a very dark red but not black. It may be that the rust formed here is a combination of the various iron oxides and that's why it appears very dark red.

As I mentioned previously, if the spindle supports were painted, it was done prior to St. Louis (where the the shock mount shaft was installed). So, if a spindle support was painted, the machined surface at the bottom of the forks would either have been completely painted or not painted, at all. In this case, the area that was covered by the shock mount shaft is obviously natural, unpainted metal. So, that means that the rest of this surface must have been the same at the beginning. As it is, the coloration on this surface appears to be identical to that on the rest of the support. So, I would conclude that no part of this support was ever originally painted.

[Gerard F.]

Re: Finish on spindle support

Jerry------


Iron oxide has many forms. These forms vary in coloration from dark red to black. The coloration on the spindle support ear appears to me to be a very dark red but not black. It may be that the rust formed here is a combination of the various iron oxides and that's why it appears very dark red.

As I mentioned previously, if the spindle supports were painted, it was done prior to St. Louis (where the the shock mount shaft was installed). So, if a spindle support was painted, the machined surface at the bottom of the forks would either have been completely painted or not painted, at all. In this case, the area that was covered by the shock mount shaft is obviously natural, unpainted metal. So, that means that the rest of this surface must have been the same at the beginning. As it is, the coloration on this surface appears to be identical to that on the rest of the support. So, I would conclude that no part of this support was ever originally painted.

Geez Joe,

I think you are right As always

Black oxide, magnetite, Fe3O4. A natural rusting of cast iron, with heat, oil, dirt, and a shortage of oxygen, it actually forms a protective coating. With more oxygen it turns to red rust, which I have a mixture of. Just like a cast iron frying pan.

The location in the picture which appears as bare metal is the part which was mated with the shock mount shaft, and so tight that they had to be hammered apart. That's probably the bare finish the spindle support had when it started out at the factory.

The black with some red in it, is not paint, as it is resistant to solvents and does not rub off. You would need to bead or sand blast it to get it off.

I wonder if anyone has any factory pictures showing the trailing arm and the factory finish on the spindle support.

So from this thread, I looks like I won't be getting under the car to paint the new spindle supports. Maybe I should have put a clear coat on them when I put the new trailing arms on.

[Joe L.]

Re: Finish on spindle support

Geez Joe,

I think you are right As always

Black oxide, magnetite, Fe3O4. A natural rusting of cast iron, with heat, oil, dirt, and a shortage of oxygen, it actually forms a protective coating. With more oxygen it turns to red rust, which I have a mixture of. Just like a cast iron frying pan.

The location in the picture which appears as bare metal is the part which was mated with the shock mount shaft, and so tight that they had to be hammered apart. That's probably the bare finish the spindle support had when it started out at the factory.

The black with some red in it, is not paint, as it is resistant to solvents and does not rub off. You would need to bead or sand blast it to get it off.

I wonder if anyone has any factory pictures showing the trailing arm and the factory finish on the spindle support.

So from this thread, I looks like I won't be getting under the car to paint the new spindle supports. Maybe I should have put a clear coat on them when I put the new trailing arms on.

Jerry------


A "mist" coat of a satin or low gloss clear will preserve them and will be pretty hard to detect.

The big problem: the original, "from-the-mold" appearance of cast iron is pretty difficult, if not impossible, to re-create. So, while you can preserve a rust-free casting, it's almost impossible to re-create the original finish appearance to preserve. But, cleaned up as you have it and with a "mist" coat of satin or low gloss clear is about as close as you can get.

[Mark G.]

Re: Finish on spindle support

Gary -

I wiped off the spindle support area with Prepsol and this is their condition. The rear wheel bearings have not been changed but I can't rule out that previous owners may have coated these surfaces.

Mark

[Mark G.]

Re: Finish on spindle support

Mark------


Thanks. This sort of information is the kind that's extremely interesting to me and I mean EXTREMELY.

For clarification, is the Chevrolet nodular iron foundry the one sort of "across town" from the gray iron foundry and later called something like "Casting Technology Center"?

When I was last in Saginaw about 20 years ago, this foundry was operating. However, there was another foundry that was located, basically, "across the road" from the gray iron foundry that was closed and looked like it was long closed even at that time. As I recall (I've got photos here somewhere) it was like a very large rectangular building with a "tear-drop" shaped water tower. It seems like someone told me it was a GM foundry that was only in operation for a short time. If I've asked you about this before, please forgive me.

Joe -

The Casting Tech. Center was at Malleable Iron CFD on the South side of Saginaw. Grey Iron had the Advanced Development Lab ADL or Experimental Foundy, later it was named Casting Development and Verification Center CDVC.
Grey Iron GIF 1912 and Nodular Iron NIF 1966 were Chevrolet Foundries on the North side. UAW Local 668 represented both plants which was
unique at the time. Nodular closed around 1989 along with Chevy plants Tonawanda, NY and St. Catherines, ONT.

Mark

[Joe L.]

Re: Finish on spindle support

Gary -

I wiped off the spindle support area with Prepsol and this is their condition. The rear wheel bearings have not been changed but I can't rule out that previous owners may have coated these surfaces.

Mark

Mark-----


I expect that these were originally painted. Note also how well the paint has survived all these years and how little rust-through is evident. I think that when you disassemble these you'll be able to tell more about the painting. It will be especially interesting to note if all machined surfaces are free of paint.

So, I expect that the change occurred when, as you mentioned previously, the foundry change occurred for 1967. This is quite interesting for a number of reasons. Presumably, the painting of the supports was not done at the foundry and this would certainly be the case if the machined surfaces are unpainted.

If the machined surfaces are unpainted, then that means that the castings were painted subsequent to casting but prior to machining. So, they were either painted at some outside vendor (as is done today with all cast iron engine blocks and cast iron heads in a system called "component painting") and then shipped to a Chevrolet facility for machining or they were painted and then machined at some Chevrolet facility. It's also possible that both the painting and machining were done at some outside vendor facility. After all, the set-up and machining of these supports would have been a very specialized operation compared to ordinary passenger car parts and it might not have been economical for Chevrolet to set up to do it. If the machining was done at a Chevrolet facility, I expect it would have been Chevrolet-Warren.

But, then another question arises: why the apparent change from painted to non-painted apparently coincident with the foundry change?

[Joe L.]

Re: Finish on spindle support

Joe -

The Casting Tech. Center was at Malleable Iron CFD on the South side of Saginaw. Grey Iron had the Advanced Development Lab ADL or Experimental Foundy, later it was named Casting Development and Verification Center CDVC.
Grey Iron GIF 1912 and Nodular Iron NIF 1966 were Chevrolet Foundries on the North side. UAW Local 668 represented both plants which was
unique at the time. Nodular closed around 1989 along with Chevy plants Tonawanda, NY and St. Catherines, ONT.

Mark

Mark------


Thanks very much for the information. So, if I understand you correctly there were once FOUR separate GM foundries operating in Saginaw. These were:

Saginaw Gray Iron (now SMCO)

Experimental Foundry (located near Saginaw Gray Iron)

Nodular Iron

Malleable Iron (casting technology center)


I thought there were only three as I thought that malleable iron and nodular iron were the same foundry or, at least, co-located.

I think the experimental foundry is the one I saw on my last visit to Saginaw about 20 years ago. I do recall it was near Saginaw Gray Iron and it was shut down at that time. Is it still standing or has it been demolished? I can't find it on Google Earth.

If I've got this figured out right, then the only cast iron foundries that GM currently operates are:

Defiance, OH Gray Iron

Defiance, OH Nodular Iron

Toluca, Mexico Gary Iron

If so, then any malleable iron or ductile iron castings that GM uses must be obtained from outside vendors?

[Gary B.]

Finish on spindle support; painted thru '66?

Mark-----


I expect that these were originally painted. Note also how well the paint has survived all these years and how little rust-through is evident. I think that when you disassemble these you'll be able to tell more about the painting. It will be especially interesting to note if all machined surfaces are free of paint.

So, I expect that the change occurred when, as you mentioned previously, the foundry change occurred for 1967. This is quite interesting for a number of reasons. Presumably, the painting of the supports was not done at the foundry and this would certainly be the case if the machined surfaces are unpainted.

If the machined surfaces are unpainted, then that means that the castings were painted subsequent to casting but prior to machining. So, they were either painted at some outside vendor (as is done today with all cast iron engine blocks and cast iron heads in a system called "component painting") and then shipped to a Chevrolet facility for machining or they were painted and then machined at some Chevrolet facility. It's also possible that both the painting and machining were done at some outside vendor facility. After all, the set-up and machining of these supports would have been a very specialized operation compared to ordinary passenger car parts and it might not have been economical for Chevrolet to set up to do it. If the machining was done at a Chevrolet facility, I expect it would have been Chevrolet-Warren.

But, then another question arises: why the apparent change from painted to non-painted apparently coincident with the foundry change?

Joe,

So is it you belief that the spindle supports were painted up thru '66 and then not painted starting with the '67 model year?

Gary