Plating suspension parts....

[Cliff Beer]

My '02 CAV is getting a much needed suspension upgrade which includes fabricated steel uprights (front and rear) to replace the alloy uprights which aren't exactly "track worthy" due to some inherent design limitations. I'm also installing new lower A-arms in the rear (with better geometry).

Most of the original suspension pieces (upper/lower A-arms in front, and various adjustable links in rear) were plated with what appears to be chrome. The plating job wasn't great as many of these pieces have some surface marks and in a couple small places the plating has peeled away.

I'd like to get these pieces re-plated with the primary goal being corrosion resistance. If the best way to achieve this is with heavy chroming that's just fine with me, appearances ("bling factor") don't really matter. In other words, what's the hardest wearing, most durable finish that can be used here? I'm guessing it's chromium, applied with a lot of care at a good plating shop.

Is there anything to be aware of? Does chroming somehow negatively affect the metallurgy from a strength/brittleness standpoint in a significant way? Is there a different finish that may be better? Nickel?

While I like the look of powder coating, I'm not a big fan of it for suspension pieces given the occasional rough wear they get.....whoops, just dropped the lead hammer used to take off the tri-spinners on the upper A-arm....

Any advice/help is much appreciated.

ps. I know there was a similar thread a year or two ago but it didn't really answer the above questions (seemed to be more focused on appearances).

 

[Rick Muck- Mark IV]

Chrome is banned by most sanctioning bodies as it may hide cracks and makes non-destrutive testing difficult. Either a powder coating or my choice would be a zinc or cadmium type plating. Cadmium is hard to come by nowadays as it is rather toxic.

 

[Dalton Veitch]

As well as hiding cracks, chroming tends to initiate them. The plating process causes hydrogen embrittlement of the steel surface and this, plus the hardness of the chromium skin (compared to the ductility of steel), may initiate surface cracking in a stressed or flexing member. Of course, the parts may be fabricated robustly, and loaded in a way that doesn't cause any undue stressing or flexing, such that the chrome plating is OK. But it is not a good thing in principle.

 

[JohnMcL]

Generally, it is bad practice to use any kind of covering that hides the surface and welds of safety critical parts like suspension components. Search on Keyphos for useful info. Look here http://www.sandwell-uk.com for stuff on anti-corrosion coating for race/road suspension parts.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>

 

[andys]

Electroless nickel plating is a viable option; doesn't promote embrittlement in the weld areas. It's not as blingey as chrome, but decent enough for improved corrosion resistance. Being not as thick as chrome plating, it doesn't tend to hide a crack, although critics will powder coat suspension pieces with a thick coating of paint and think nothing of it.

Andy

 

[Chris Hale]

Cliff, be very careful when chroming any suspension parts as I have just experienced both my lower wishbones bending and this was most likely due to hydrogen embrittlement.

 

[Howard Jones]

I recommend a light grey primer and then one coat of high quality silver header paint. For all the reasons concerning detection of cracks. The silver will provide some contrast to the crack should it appear and will look good enough to keep you happy. Power coating is probably the best way there is to hide a crack until it's too late. Better even than chrome as it tends to stretch over the crack and thus hiding it.

 

[Cliff Beer]

Thank you gents. Well, no perfect solution here (as usual, life is messy....)...

Powder coating tends to hide cracks really well. Chroming encouragess brittleness.

Thin coat of spray bomb paint?

The A arms are very, very beefy, I'll say that for them. Not going to win any awards for lightness. I don't know exactly what's the wall thickness, but it feels like it's about 1/2 inch!

On a related note, does anybody know how the ball joints come out? I'm guessing they're pressed in from one direction or another. Anybody know if they're pressed in/out, and what direction they come out?

Thanks.

 

[Mick Ridley]

Hi Jim,

If you look at the thickness of the boss, that the Ball Joints are pressed into, you will be able to tell which side they were pressed in from.

As the boss in thinner at the bottom,, it is that side they were pressed into.So I would push them down, and out......Maybe someone else can confirm this

Jim do you have any pics of your new uprights we can see ?

Mick

 

[Mick Ridley]

Cliff,

Sorry I dont know why I called you Jim.......

I was assuming they were bottom "A" arms, but they may be top ones, eitherway push towards the thin part of the boss, to push them out

Sorry for the confusion

 

[Tim Kay]

I, like Chris H, have had my chromed lower a-arms bend. Two sets in fact. I m not completely convinced it was due to hydrogen embrittlement. After dissecting the bent a-arms I found them to be fabricated from rather thin wall mild steel.

OTOH, I had a steering arm break that was 90 percent suspect to hydrogen embrittlement. Needless to say no more chrome for me on critical parts that control the car. I am going to powder coat though.

 

[Pat]

Hi Cliff, if you got the uprights from CAV Canada, they just bolt up to the existing ball joints. Unless there is play, why replace them? When I upgraded my CAV front end, I took the a-arms to a plating shop and they said the best thing is to give them a good polish and not worry about replating. That way, you won't miss any cracks etc. As you indicated, they are quite heavy and pretty stout. They came out looking new.

 

[Cliff Beer]

Hi Cliff, if you got the uprights from CAV Canada, they just bolt up to the existing ball joints. Unless there is play, why replace them? When I upgraded my CAV front end, I took the a-arms to a plating shop and they said the best thing is to give them a good polish and not worry about replating. That way, you won't miss any cracks etc. As you indicated, they are quite heavy and pretty stout. They came out looking new.

Hi Veek,

Thanks, yup, the front and rear uprights from Ian at CAV Canada.

That's a good suggestion, and that's what I would be doing except that on the lower A-arms the chrome plating has come off in a few spots and there's actually some corrosion and pitting started. I could probably take the wire wheel to it and get the crome off and clean out the pits...that certainly would be easier! Will check it out and report back.

Thanks gents.

 

[Cliff Beer]

Cliff,

Sorry I dont know why I called you Jim.......

I was assuming they were bottom "A" arms, but they may be top ones, eitherway push towards the thin part of the boss, to push them out

Sorry for the confusion

Thank you Mich. You're very observant...more observant than me obviously! What you say makes total sense and no doubt that's how they go in and come out.

Appreciate the heads up!

 

[Phil]

Cliff: Those ball joint sleeves look like the ones we use for the threaded lower ball joints. I can't see enough detail but they might just thread out.
If not, on the lower arm they will press out to the bottom as the upright pulls up on the lower joint. You need to set up a little fixture to push those joints out, taking care not to push on the bolt, but the body of the joint.
Cheers
Phil

 

[Pat]

Cliff, the only drama I had in the front upgrade was getting the stub axle nut off. 600Ft/lb air gun didn't even annoy it. I eventually had to machine it off. Hopefully you won't have the same problem. If you do, the replacement nut is off a BMW 3 series.

 

[Cliff Beer]

Thanks Phil, turns out (no pun intended...haha) that they're the press-in variety, but thank you for the suggestion. I stared at them long and hard before putting the squeeze on 'em. All four ball joints came out OK.

Thanks Veek, yes, have been wrestling with the stub axle nuts! I have a one inch impact wrench which is supposed to deliver 1,400lbs of torque, but we'll see. Thanks for the tip on the replacement part!

 

[Pat]

Cliff, just in case, part number with BMW: 31211128336

Hopefully Murphy's Law will take effect and since you have it you won't need it

 

[Cliff Beer]

Thanks Veek! I'm making slow, but sure, progress here. Obviously this thread has been a great resource!

Does any one know what ball joints CAV uses? Also from a BMW perhaps? My four ball joints look to be in OK shape but I may as well replace with new if I'm pressing them back in.....

Thanks.

 

[Cliff Beer]

Quick update here....

So I went to see the guys at the local plating shop, and they said the most durable finish to put on suspension parts like that is......powder coat! Chroming or other plating finishes apparently won't last as long as powder coat in that kind of environment (exposed to road crud).

Now, I'm not going to go vintage racing in my car...the local vintage racing association here in the Pacific Northwest (SOVREN) doesn't allow any car onto the track that a) was built after 1970, and b) lacks authenticating paperwork. It doesn't matter how good a replica your car is, or who it's licensed by, it ain't goin' on the track. So, what I'm left with is club track days (alfa club is particularly good) and for that a powder coated A-arm will be just fine. For my own safety, I'll be inspecting these A-arms very closely, and hopefully seeing anything funky despite the powder coat.

Will post pics when I have the A-arms back from the shop and the front suspension all back together.

Thanks.