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Discussion in '1970 - 1973 Specific' started by 67johnny, Oct 20, 2017.
I’d like to see pics of your 70 Z28 too. Please share them with us.
Problem with the Eastwood aerosol is that is a paint. Paint is pretty much on the surface only and its adhesion is not as good as the zinc phosphate which penetrates the surface. It is easier though, but rarely is easy better. It depends on what you want. Hood hinges are a pain with paint as the rubbing surfaces scrape the paint off. Paint DOES prevent rust better. Phosphating requires upkeep, but not so bad with the right rust preventative like Chuck outlined. Most of these cars don't see the weather like a daily driver does. If your is a daily driver, I would recommend a good epoxy primer and then a topcoat.
The difference in phosphate finish has to do with many variables, not the least of which is the type of metal and if its heat-treated, but this is technically correct for automotive restorations. There ARE supposed to be differences between parts, but not so much within a given part. You will never get that with paint.
Here is an example of two rods I did just today. Same solution, same prep, same time(in the tank together). The 5618 rod is noticeably darker than the 5624 rod.
View attachment 46513
Dave, Strange to me that the two shift rods would turn out so different.....
Ive never seen OE rods OR restored Manganese Phosphate Rods that were
anything other than dark gray similar to your lower pic.....All of my misc pics
are of show cars or at least sunny day, no rain cars....
Any good owner NEEDS to keep applying Fluid Film on any of the Phosphated, Zinc
Plated parts, fasteners everything..............
Yeah, it was strange to me too on the 5618 rod. All the other shift linkages and even the hood springs I did at the same time came out a lighter grey like the 5624 rod. I even re-glass beaded it and re-phosphates it and it came out exactly the same. It is very even Not blotchy or anything like there was contamination. It must be the metallurgy.
Then I compared it to this one
And it looks almost exactly the same.
Maybe the steel varied a bit from different vendors. There probably wasn't a second thought given to the color when these things were made.
Dave - agree with everything you've posted and I've seen similar manganese phosphate results on different items. I've noticed a big difference on a steel piece made from the same material but has been spot hardened around specific bearing surfaces. As I recall, the phosphate seems to take a darker appearance on the hardened section than on the non-hardened surface. My point is exactly as you noted...difference metallurgy yields different results. Once it stops fizzing...the conversion is done and it is what it is.
I actually blasted my bolts and sprayed them with Zero Rust before reinstalling them.
For my own knowledge, I understand that most of the components OTHER than bolts to be zinc phosphated with bolts-fasteners to be typically manganese phosphated. Is this also your understanding?
Since this is not well documented for 2nd gens (at least anywhere I can find) I draw my reference to this from the 1st gens:
I know this is possibly prone to mistakes, but in lieu of something similar for 2nd gen's, it is the best I have found. I guess my belief is that for parts that were not changed from the first gen to second gen (especially 1970 second gen - example: engine lift hooks or standard wiper motor) the supply base probably stayed the same and so the finishing methods probably stayed the same. Unless I find photos from originals such as the low mileage former Charley Lillard car that differ with this, its what I have to go on.
Do you have other references I am not aware of?
Some of my parts turned out the same way Dave shows in post #12. My reverse lock-out/back drive linkage & frame bracket turned out lighter gray then my shifter rods. I always thought that maybe they were plated incorrectly but after seeing your pictures probably not.
Dave - I agree the fasteners are going to be typically manganese phosphate or silver cad or chrome (interior sheetmetal screws), depending on the application. I also believe most non-hardware items that weren't painted were manganese phosphate, silver cad, gold cad, black oxide or natural steel. The difficult part is that 2nd Gens are almost 48 years old and all of the above finishes age and change appearance to some degree. As an example, I bought an original paint 70 sport Coupe that was born in and lived its' entire life in SoCal...so rust was basically a non-issue. I used it as a parts car for my 70Z restoration so I removed virtually every nut and bolt. Many of the bolts actually appears light gray as did the hood latch and hood hinges...but once removed, the surface areas protected by an adjoining section of sheetmetal showed darker....aka Manganese.
I checked out your link to the CRG above and noted three things...1) many of the items have multiple acceptable finishes, 2) they only specified "phosphate", but were not specific whether it is manganese or zinc and 3) some of the finishes I do not agree with. For example, the dip stick tubes for SBC in 70 would have been natural for Norwood and black for Van Nuys...but these are minor items.
Chuck's pics of the shifter assemblies are interesting as well...note the standalone shifter is manganese phosphated and the assembly mounted to the trans is silver cad. My understanding from Pete Serio is that Hurst changed the shifter body finish from silver cad to manganese phosphate in March-ish of 1970...so both could be correct depending on the shifter body date.
I am likely overlooking some items and some may outright disagree. That's okay as I've been wrong before and am always open to other inputs and corrections .