Nut & bolt finishes for '70

[Alan D.]

Re: Nut & bolt finishes for '70

Steve, I'd advise looking at the chemical dip process a lot more before using. These are acid based for the most part which I understand (only from past posts) can cause a change in the hardness rating of bolts. Some of these dips may be OK, but others ??

[Joe L.]

Re: Nut & bolt finishes for '70

Joe,

Black oxide was most commonly used over stainless steel on exterior trim fasteners. It was also used on the stainless interior fasteners of some cars that were available in converible models. Visually, its sometimes tough to tell this finish from the multi-layer black used on non-stainless screws for such applications.

I guess its possible to service all these parts with the non-stainless multi-layer finish, but I'd be very surprised if some service fasteners for such applications were not stainless with black oxide.

Mike

Mike-----


Yes, there are/were a relatively small number of black-oxide finished machine screws and tapping screws available in SERVICE and probably used for trim applications. Many of these were black oxide over stainless steel, as you mention. However, I can't find any bolts available in SERVICE for the last 20 years, or so, that were black oxide finished.

It's also very possible that there were many more machine screws and tapping screws of black oxide finish used in PRODUCTION. Fasteners available in SERVICE are just a small fraction of those used in PRODUCTION. But, given the fact that I can find no black oxide-finished bolts available in SERVICE, that implies that there were likely few, if any, used in PRODUCTION.

[Michael G.]

Re: Nut & bolt finishes for '70

Joe,

I agree. Black oxide was not considered a normal machine screw (or bolt) finish, as it had virually no corrosion resisitance and lousy frictional characteristics. There are not many non-tapping screws with this finish. I don't think I ever saw it specified for non-stainless, machine-threaded fastener.

Regarding "black zinc": The black color resulted from a black chromate over the electroplated zinc. Usually it was readily identifiable by its non-uniform, slightly "iridescent" appearance. I hope that helps.

Mike

[Steve G.]

Re: Nut & bolt finishes for '70

Based on replies, I am getting concerned about the chemical dip process. Before spend the money on a beadblasting cabinet... has anyone had luck using a tumbler to remove rust on the hardware, and then doing the plating? Scott at Palmetto says that is not a good alternative. But thought I'd check with you all.

Also, he strongly suggested I do all the hardware in gray phosphate as it comes out a dark gray. That was surprising to me as I thought I would need gray phosphate for the toe boards (and hood hinges if I do those), and black phosphate everywhere else. Thoughts?

[Patrick H.]

Re: Nut & bolt finishes for '70

Based on replies, I am getting concerned about the chemical dip process. Before spend the money on a beadblasting cabinet... has anyone had luck using a tumbler to remove rust on the hardware, and then doing the plating? Scott at Palmetto says that is not a good alternative. But thought I'd check with you all.

Also, he strongly suggested I do all the hardware in gray phosphate as it comes out a dark gray. That was surprising to me as I thought I would need gray phosphate for the toe boards (and hood hinges if I do those), and black phosphate everywhere else. Thoughts?

Steve,

I've tried chemical, I've tried tumbler, I've tried wire wheel and I've tried bead blasting. The best is bead - actually, even better is sand - and the next best is wire. Wire will give you a smoother finish, but with phosphate you want a rougher finish to "bite" into so I'd recommend sand. I have refinished hundreds of bolts and have had plenty of opportunity to play with methods.

Also, you are correct on colors. I've used Palmetto's product and their black (i.e. manganese phosphate) is dead nuts correct. Scott is not correct on this.

I also think that more hood latches (not hinges - those are silver) look darker than what most zinc (gray) phosphate kits give you. Many I've seen replated and then had a chance to judge appear more light gray than any of the originals I own or have seen. I've never tried it but suspect a 50/50 mix of zinc and manganese would give the correct shade.

Patrick

[Alan S.]

Re: Nut & bolt finishes for '70

Hi Steve ,
Here's a picture of a latch plated in zinc phosphate. As Patrick notes it is quite light. I think the blackout background and the flash exaggerate the lightness of the color a bit.
Patrick, your thought of using a combination of zinc and manganese... do you think that's possible or were you just musing.
Good luck Steve, I think you'll be surprised at the results you can achieve. I'll send the 66 chassis article this afternoon; look for it.
Regards,
Alan

[Patrick H.]

Re: Nut & bolt finishes for '70

Hi Steve ,
Here's a picture of a latch plated in zinc phosphate. As Patrick notes it is quite light. I think the blackout background and the flash exaggerate the lightness of the color a bit.
Patrick, your thought of using a combination of zinc and manganese... do you think that's possible or were you just musing.
Good luck Steve, I think you'll be surprised at the results you can achieve. I'll send the 66 chassis article this afternoon; look for it.
Regards,
Alan

Alan,

I suspect it is entirely possible to make a mixture of the two but as stated I've never tried it. As you show in your picture the zinc phosphate appears lighter than an original piece. On my 72 the hood latches appear relatively dark and a manganese phosphate would replicate this. Others I have seen appear just a bit lighter but not as light as yours - or other zinc ones I've seen fellow members refinish - appear.

Patrick

[Terry M.]

Re: Nut & bolt finishes for '70

Alan, if you are going to refinish the hood latches anyway, try putting some oil on them before you refinish them. I know it will make the clean-up harder if you have to replate them -- but a common specification in the 1960's was "phosphate and oil." It may be the oil that makes it darker.

[Jeffrey S.]

Re: Nut & bolt finishes for '70

Steve:
Don't get discouraged by thinking you need to invest a fortune in auxilliary supplies and equipment to get good results. The biggest investment is in your time to get over the learning curve. You will have to make a committment to trying by buying the chemicals which are not outrageous but do cost. I have been using the Caswell black oxide and the Shooters Solution black phosphate and have gotten excellent outcomes with both. The phosphate gives a more textured surface and the "sparkles" associated with hood latches, etc where the oxide is blacker and smoother. Rust removal is also not so complicated. You can buy a small sand blaster that can blast directly from a pail of sand (outside) for doing small fasteners without a cabinet. Rust removal chemicals are now available that say they don't use acids (my guess is that they don't use phosphoric acid but may use some sort of citric acid) I will post the name of the one I use but it is in my shop and I don't have it here. The chemicals work great for smooth finishes like zinc, black oxide, etc. When I want a "cadmium" like finish using Caswell's "CopyCad" I like to sand blast to get the texture. The same with the black phosphate. You need to experiment to find which works for you. When you get stumped, ask for help here on the board and we will be glad to help. But most of all "Just Do It". Just my 2 cents.
Jeff

[Jeff B.]

Re: Nut & bolt finishes for '70

Earlier on, with my current 64 roadster restoration, I went throgh the same issues. One thing I found is that most idustrial plating shops don't do black phosphate anymore. I have a favorite plating shop called EPS (Electro Plating Specialists) in Oakland CA that I had a long talk with. They do a lot of Aircraft botls and are know for great Cadmium plating. They offer both Cadmium and Zinc in colors, including black. Both Cadmium and Zinc offer superior protection to a phosphate finish. For the bulk of my bolts (about 500 of them) my solution was to have them done in two basic finishes. All bolts that were silver finish got what's called "clear cadmium" (the best protection) and all bolts that were black finish got the the black zinc finish. The black zinc finish is a bit more glossy than the black phosphate was but it will hold up much longer. The other good thing about using an industrial plating shop is that their chemical stripping process is really good and my bolts came out really detailed, especially the headmarks. Since that time I have also gotten in to doing my own finishes for one-off items. I use the Casewell (Copy Cad) products, but to do it correct there is quite an investment. You really need a blast cabinet, the plating kit, and for many finishes, a good regulated / adjustable DC power supply. I bought a 10 amp power supply that has adjustable voltage and current and it was about $300.00 A good power supply is key to a good repeatable finish process.

If you use an industrial plating company, make sure you catalog your bolts before you send them. Unless you specify otherwise, they will do the bolts in bulk and they will send them back all mixed up. I laid each group of bolts out on a white marker board (one group at a time) together with any washers and nuts and used a dry erase marker to write down bolt info, location, size, and headmarks next to them. I then took a digital picture of each group and named the picture after the bolt group. This made sorting them out much easier. (I also made a spreadsheet and linked the pictures to it but that's way over the top). I sent my bolts to the plating shop in just two containers, one for the black bolts an one for the silver bolts. The total cost for all 500+ bolts was $185.00 and the finish was fantastic.

[Chuck S.]

Re: Nut & bolt finishes for '70

Based on replies, I am getting concerned about the chemical dip process. Before spend the money on a beadblasting cabinet... has anyone had luck using a tumbler to remove rust on the hardware, and then doing the plating? Scott at Palmetto says that is not a good alternative. But thought I'd check with you all.

Also, he strongly suggested I do all the hardware in gray phosphate as it comes out a dark gray. That was surprising to me as I thought I would need gray phosphate for the toe boards (and hood hinges if I do those), and black phosphate everywhere else. Thoughts?

Before I start on your questions, my curiosity overwhelms me...What the devil is a "toe board"?

I would agree with Scott on blasting, if only because you have tons of fasteners to phosphate, and tumbling will be slow. For a car quantity of large fasteners, you'll need a tumbler large enough to do a satisfactory job. There will be the temptation to overload the tumbler to speed up the process, and the net result is you'll probably slow it down further. Also, I'm not sure, but media consumption may be rapid when tumbling steel. For screws and other fasteners under about #10, tumbling is likely to be a very good approach. Handling screws and small fasteners in a cabinet using heavy rubber gloves is, to say the least, frustrating...you'll probably drop half of them into the bottom of the blast cabinet.

If you don't already own a tumbler, I expect the difference in cost between a good tumbler and a small Chinese bead blast cabinet will be insignificant. You don't have to buy a professional quality cabinet like TP Tools for one job; remember that the blast cabinet is only a means to contain the media while maintaining visibility. If you're going to do any more restorations, then the TP Tool cabinet will be worth the money. Once you own one, you'll wonder how you got along without it.

I don't agree with Scott on "one phosphate color fits all"; if you're going to the trouble to restore a Corvette to original condition, then take your best shot at getting the color exact. As Terry said, the ideal situation was to have assessed and recorded, as best you could, the finish remaining on the fasteners when you disassembled the car; but that advice will have to wait for your next restoration if there is one.

Earlier comments are correct...you can probably make some gross assumptions on chassis fastener finishes and be correct most of the time. Based on my observations, I found more black oxide than others have said, but my observations could have been compromised by condition (Sometimes, you have to take your best shot). On a car that has a lot of rust, your toughest challenge will be to separate formerly black phosphate fasteners from formerly natural steel; but fortunately, there aren't many natural fasteners either. My observations classifed 70 fasteners as black phosphate, dark gray phosphate, medium gray phosphate, black oxide, natural, and zinc.

Phosphate color on components can vary slightly from car to car, but remember that phosphate color depends on metallurgy of the part and the cooking time in solution, as well as the chemical used for the solution. Suppliers would have followed virtually the same process for every batch, using the same chemicals, to provide virtually the same color for every part of a given type. As in any manufacturing process, I'm sure "the process" was modified by human intervention occasionally.

For shades of black phosphate, manganese phosphate is/was used; for lighter shades of gray, zinc phosphate was probably used. For example, you say the hood latches are gray phosphate...perhaps this is semantics, but I suspect they are actually "black phosphate" with less time in solution; it's hard to get anything as dark as the hood latches with zinc phosphate.

Rusting of fasteners after bead blasting and before parkerizing is a non-issue in my opinion. If you live in a humid climate, you can put perfectly clean, wet parts into the hot solution by dipping parts bead blasted earlier in dilute muriatic acid, followed by a dilute phosphoric acid dip just upstream of the parkerizing solution. The phosphoric acid dip may not be necessary, but I figured since the solution was phosphoric acid based, it would be a good idea to try and remove as much muriatic acid as possible to reduce contamination.

There will be the usual concerns about hydrogen embrittlement from the different steps, but you'll have to do your own research on that subject in the archives and make your own decision. My personal opinion is that stress cracking is much less of an issue for parkerizing than for electroplating.

[Terry M.]

Re: Nut & bolt finishes for '70

Before I begin to address your questions, my curiosity overwhelms me...What the devil is a "toe board"?

Chuck:
Heat shields under the footwells. You know, the ones that block the body # and the body options written on the driver's side.

[Chuck S.]

Re: Nut & bolt finishes for '70

Chuck:
Heat shields under the footwells. You know, the ones that block the body # and the body options written on the driver's side.

Ahhhh...thanks, Terry.

As I recall, those shields are a nice medium gray. The dark black phosphate sometimes provided by repro vendors is INCORRECT, INCORRECT, INCORRECT!!!! (Opps, ah, uh...I mean "not typical factory production".)

Happy holidays, Terry.

[Terry M.]

Re: Nut & bolt finishes for '70

On my 1937 Cadillac that part of the floor is called a "toe board." I guess being bilingual means something different to some of us.

Merry Christmas to you too Chuck. Thanks for all your help this year.

[Alan D.]

Re: Nut & bolt finishes for '70

FYI - on the popular chem dip;



RidRust now called Safest Rust ph=5.25 ($35/gal)

Rust Clean by Amazing One in Howell, MI gone
Evapo Rust see orisonllc.com or orisonmarketing.com ph=6.1 ($21/gal)
CLR ph = 2.0
ZEP at Home Depot ph = 1.0

Once parts are cleaned if they rust up a little before plating I would use one of the high ph products to clean up rust and then rinse with distilled water