What are the best ways to protect new nickel plated suspension parts from corrosion?
I just purchased new wishbones from Universal and will soon have replated rockers from Prince. I would really like to keep them rust free for many years!!! The car is an autocross car stored in a garage BUT it is towed on an open trailer.
Wiping down with WD is helpful in two ways - it's a great way to clean and shine the nickel and it takes care of surfaces that didn't get plated. Here's the deal:
Nickel should not corrode, at all, especially if electroless nickel is the topcoat. I did a lot of plating development in the 80's to protect parts against mil-spec salt fog environments (evidently, the presence of atmospheric SO2 now makes this test even harsher). Electroplated nickel is differentiated from chrome in that the surface at the microscopic level is fairly contiguous. If you look at chrome under a microscope, you'll see a surface that looks like a dry lake bed, with lots of little fissures. Moisture penetrates here and develops into the pinhole rust that eventually pops the chrome off.
Nickel doesn't have these fissures to get the process started.
However, most electroplating processes start with a copper flash to raise conductivity and promote adhesion. Copper is extremely active and corrodes quickly. The copper is exposed where the electrodes are attached to the part - so during the copper part of the process there's bare steel somewhere and during the nickel part of the process there's some bare copper somewhere. You can fix this problem by moving the electrodes halfway through the process, but that's a PITA and almost nobody does it. Those surfaces will still corrode. So if you can identify those spots and touch them up with some metallic paint you'll be ahead of the game.
Electroplating won't "throw" into cavities unless very special tooling is made (making electroless better for complex shapes, electroless deposits like snow on your lawn). So if you have pockets, like the insides of flanges and gussets used to attach shocks or pushrods to lower a-arms for example, there's not going to be plating there, and a bit of paint goes a long way. If that pocket is going to hold moisture, a couple of .050 holes drilled in it to promote draining will weaken the part less than accumulating rust and the loss of thickness. A good example of one of those spots is where the bottom end of the pushrod attaches to the front a-arms of 90's van diemens. They notch the gusset between the legs and braise a couple of tubes to hold the bolt, leaving a deep pocket inside the a-arm to collect water.
Lastly, the chemicals used in electroplating promote corrosion if left in place and get continuous re-activation by moisture. You usually dip in some kind of acid, either SF, HF, or N, or HCL, as a means of cleaning the surface and etching it. The nickel and copper solutions are CN based. These solutions get inside your parts and continue to leach out for years. Best to thoroughly clean everything with a hot water wash after you get them back, maybe with a little soda in it to neutralize whatever is left. Use bore brushes on holes and tubing and it helps to run a cleanout tap through threaded holes all the way to the bottom first. Throw the finished parts in your oven at 220 deg for an hour or so and then follow up with tube oil inside.
Sometimes platers do a good job cleaning the parts, but most of the time they don't. I plated that tubular reinforcement that ties the rockers into the top of the gearbox on a 1995 van diemen. It had a couple little gas relief holes drilled in the parts that I forgot to have masked. Six years later they still weep plating goo because the holes are too small to really get in and clean stuff out. But they sure let the chemicals in!
I prefer shrink-tube to the other "spiral" stuff, which traps dirt/grit.
Watch the use of RTV, those that have that "vinegar" smell, are corrosive and those gasses will be trapped inside the parts.
I use anti-sieze on the rod ends because it seems like after plating, the combination of chemical cleaning and re-tapping the holes makes for an extremely rust-prone surface.
I have some spare a-arms for my old royale that have snapped-off rod ends rusted in place. I originally thought they were the result of crash damage until I saw the spiral fracture site - and those were 3/8"!
I use Velcro (the soft, fuzzy side) to protect s/s braided lines and the components they rub against, applied to the adjacent component, not the line. Eliminates the problem, is pretty cheap, won't melt and definitely looks better than cheap plastic loom or the classic zip-tied split rubber hose protection.
I believe this practice is used by many pro teams; also great for vibration isolation.
Last edited by a. pettipas; December 18th, 2010 at 1:41 PM.