Anodized Alluminium

[Markbhai]

Hi.

I am self restoring a 1966 230 SL and learning along the way. I have a soda blaster to clean all of the parts but was wondering if anyone has anodized the aluminium such as fuel lines etc.

I have seen instructions to do this myself but they relate to adding colour to get the yellow hue.  I am wondering if anyone has any advice on achieving the correct colour?

Mark.

[cfm65@me.com]

Hi Mark,
As far as I know, the alu parts are not yellow. Annodized alu is normally a silver colour. Although, I think a wide range of modern colours are available.
The steel parts, nuts and bolts, etc are electroplated and part of the procedure is to neutralise the plating process by dipping the parts in a special fluid.  The  fluid/process is called 'yellow' or 'bright' passivate, which ever one you choose, leaving it with a golden or silver colour.
GOOGLE is your friend. Also search this forum for photos and advice on which parts should be plated and yellow, also which parts should be painted black or body colour.
Regards
Chris

[Markbhai]

Thanks Chris.

I have see pictures with fuel lines and linkages a yellow hue so given your advice I suspect these must be steel.   It shows how poor my knowledge is, I guess that why we enjoy this forum so and much.

I will look into the electroplating process for these and see if it would be something I could achieve rather than to send the parts away.

Regards

Mark.

[cfm65@me.com]

Hi Mark,
Yes, I am quite sure the fuel lines on a Mercedes are steel. Electroplating is not expensive here in South Africa, it might be worth your while to check prices at your end, before spending a lot of time and effort trying to do it yourself.
I suggest you take photos of all your parts when handing it over to someone else, and make sure you get every little part back from the platers.
Platers will swear blind that they do not loose parts, but it could happen and does happen sometimes.
Regards
Chris

[Benz Dr.]

We call it zinc chromate - yellow in this case. Part is zinc plated then a chromate wash is applied over top of it. This stuff has tiny pieces of chrome in it which is why it has a shiny appearance.

[Shvegel]

If you do have your fuel injection lines re-plated you have to come up with some way of plugging the ends as the corrosive nature of the plating can cause the small diameter lines to corrode shut. 

[hkollan]

If you do have your fuel injection lines re-plated you have to come up with some way of plugging the ends as the corrosive nature of the plating can cause the small diameter lines to corrode shut.

Standard MB lug bolts with 12x1.5 threads will do the job if you decide to plug the fuel lines before plating them.

Hans

[winston the browndog]

Mark ,
  The fuel lines are Cad plated , which is short for Cadmium electro plating . The yellow color is called Cad 2  and the silver is called Cad 1. The Cad 2 is just a final dip  that is part of the process . As far as pluging up the ends , there is no need . In the plating process the fluids should not be trapped inside any areas  and it will coat  the inside as well . Cad plating is used mostly used for steel items . Make sure that the items that are plated are baked ,to relieve them from Hydrogen Embrittlement . As far as Anodizing , that process is for Aluminum , It can be done in almost any color you want .
Good luck , Paul

[wwheeler]

Hi Paul,
There are a couple of items that I don't totally agree with. I do much of my own zinc plating at home, and am familiar with the process.
1) plating will NOT cover inside pipes. Yes the plating fluid goes inside, but the electrical current that actually bonds the CAD or zinc to the metal cannot reach "hidden" areas. Areas also under the fittings at the ends of the lines will not plate either. They end up with a dull finish and is not corrosion resistant.
2) CAD plating is mostly used in aerospace where high corrosion resistance and very thin plating thicknesses are required. Most steel parts these days are zinc plated and far more common. Zinc can be silver or gold colored just as CAD. CAD is three times the cost and is very toxic, so not used often. 
3) Plated parts are indeed prone to Hydrogen Embrittlement. The only time it becomes an issue is typically on springs and parts subjected to flexing and fatigue. Again, it is an extra cost and not needed for most parts. I hope that clarifies.

[Shvegel]

Wallace,
As you stated the Zinc or Cadmium will not plate the inside of the lines.  The problem seems to be with the acids in the cleaning or plating process causing rust in the lines and blocking the tubes.  Someone here had to replace their lines because they were totally blocked after plating.

Here is a thread on the issue:

https://www.sl113.org/forums/index.php?topic=18284.msg152945#msg152945

[wwheeler]

Correct - No plating protection inside lines, tubes or hidden areas. Most people don't see that. My understanding of the plating prep process is that the platers dip the parts in an acid. The acid burns up any old zinc or Cad plating as well as rust and goes back to bare steel providing a light etch.
NOTE: Acid will not remove paint or grease which is why DIY prep work is so important to a great plating job. Most platers start with brand new metal and are not concerned about paint or grease from old parts. That is your job.

So the acid and plating solution are corrosive. I think the damage happens after the fact though. I am not sure how thoroughly the platers rinse the parts and that probably varies. Rust will form quickly on parts that have hidden areas (not plated) and are not properly rinsed. Rust will act on bare steel (from the acid and plating solution) quite quickly.

I think a lot depends on the condition of the lines before plating. If a car sat for years with water in the gas and had rusted lines, it has a far better chance that plating could make the problems worse. I always run a solid steel wire through the lines vigorously before sending them off. Keep in mind, steel lines were plated when they were new. So the process itself isn't bad on new parts, just need to be cautious on used parts.

[mdsalemi]

The "costliness" of cadmium plating, in our realm, is probably irrelevant. The greater cost of any kind of protective plating is in the setup and lot charge.

One thing we must consider is that cadmium, like zinc, or tin-zinc, with or without the phosphate wash, is a "sacrificial" plating as opposed to a decorative plating like chrome, or gold on jewelry. However, what we are typically looking for in restoration is both, with almost an emphasis on the decorative: we want the plated parts to look good too. Sacrificial platings are designed to wear away instead of the metal they protect. Boat owners know this from sacrifical anodes on their metal engine parts. If you have a hot water tank in your home, there's a huge rod of sacrificial magnesium hanging inside the tank. As long as this is in place, and wearing away you are fine. Soon as that magnesium is gone, the water will start to attack the steel tank.

If you are doing it yourself, such as Wallace, for certain you don't want to attempt cadmium plating (unless you smoke, ride motorcycles at excessive speed, or have other self-destructive tendencies) because of the nastiness of the chemistry involved; not only do you need the cadmium metal (quite toxic) but also cadmium salts for an electrolyte solution, plus cyanide. All toxic, dangerous to handle, and I think they might be carcinogenic too.

But if you are looking for originality, cadmium (done by a pro not in your basement!) plating is the way to go; it does provide the proper look when done correctly, and has a longer life than its substitutes. That longer life doesn't mean a whole lot in today's modern engine bay where things are plastic and painted and powder coated, but when you are working with hard to replace parts that are half a century old, sometimes it is worth considering...

I've had both zinc plating done on the original restoration of my engine, and cadmium plating done a couple of years later. There's no question that the zinc hasn't aged nearly as well...and the cadmium still looks great. The reasonably bright color of the gold phosphate wash from 17 years ago has faded. The cadmium has not.

[wwheeler]

If you are doing it yourself, such as Wallace, for certain you don't want to attempt cadmium plating (unless you smoke, ride motorcycles at excessive speed, or have other self-destructive tendencies) because of the nastiness of the chemistry involved; not only do you need the cadmium metal (quite toxic) but also cadmium salts for an electrolyte solution, plus cyanide. All toxic, dangerous to handle, and I think they might be carcinogenic too.

Luckily for man-kind, I do not believe there are any DIY CAD plating kits out there. And no, I do not CAD plate at home, only zinc.

The cost of the CAD is based on batch size just like zinc. In my area zinc is $60/batch and CAD is $150/batch. So if you are doing a complete nut and bolt restoration and you plate everything at the same time, cost is irrelevant. But if you only restore portions of the car at a time, you will almost never reach max batch size. But you still get charged for the full batch. And then there are the inevitable few forgotten parts from a project that need to be plated. That is when paying for a full batch really hurts. It is then that the DIY zinc kit comes in handy.   
BTW, fuel lines and long pipes are usually done separately on racks and therefore have an additional charge separate from the batch price.

[mdsalemi]

...and one of the benefits of our forum-membership, for those that don't lurk, or remain anonymous, is to share and develop friendships.

I've sent along some parts to one of our members here, who was having cadmium plating done. My parts were merely the transmission filler tube; the cap for same; and some plates on the trunk lock assembly; when he got them back he sent them to me. In turn, at a different time, he sent all his wheel covers to me as I was having mine painted and we share 568 Signal Red as our car color...the sharing all worked great, as we split the batch charges.

So one way to avoid a batch price is to partner up with a friend! 

There's probably no shortage of those who need some plating done here. Myself included! (that old zinc needs a refresh)

[Benz Dr.]

Cad lasts longer but doesn't look as good. I'm pretty sure by the time 280SL's were in production they were using zinc chromate.

[66andBlue]

Hi Dan,
as always beauty is in the eye of the beholder.
IMO cadmium looks better than the copper-tone shine of Zn-chromate. Take a look at the photos here:
http://www.detrayplating.com/YELLOW%20SPRINGS_zincpg.JPG  and compare with:
http://www.detrayplating.com/aerospace_fasteners.html

[Benz Dr.]

That depends on who does it. I've had cad plating done and the color was very consistent and it was also very costly. I've also had zinc chromate done and it was very inconsistent which is why I went to cad plating. No one in Ontario will do cad plating so I had to go to Detroit area to get this done which was further and more bother than my current place. In the end, I found a place that does a really nice job and their quality is high. They also do all sorts of different finishes and they don't mind doing small runs.   

[wwheeler]

I would guess the inconsistency comes from two variables.
1) The amperage and time for which the plated parts are exposed to the plating bath. That effects how much material is attracted to the part to be plated. More is NOT better and more leads to a fluffy, dull look.
2) Amount of time plated part is dunked in chromate. The longer it is in the bath, the darker the color. I am not sure if longer exposure here is a bad. The chromate simply protects the plated material. And it also looks pretty.

Most people don't know, but even hardware store bolts have a chromate as well. It is called clear zinc and gives it a VERY slight bluish color. I am pretty sure all commercially plated zinc or CAD plated parts come with a chromate.