On Sat, 24 Mar 2012 10:57:03 -0700, durabol wrote:

I'm new to electroplating and was wondering if anyone could provide some
insight (and save me from reinventing the wheel) in the following
methods of electroplating an aluminium cylinder bore both for protective
reasons and also restoring a worn cylinder bore back to spec. so don't
need oversize pistons. This is for a homemade two- stroke engine, see
http://groups.yahoo.com/group/DIY_2S/ for more information.

Cylinder Bore Protective Plating:
-Hard Anodizing, high silicon aluminium, easiest -Electroless
Nickel-Phosphorous/NiP: can do it in one step, hardness close to chrome
-Nickel Cobalt: not sure if can get enough cobalt in nickel to be
useful?
-Nickel/Suspended Particles: trapping hard particles suspended in
solution into nickel plating
-Nitride: similar to how some metal tools are protected, not sure if
possible/practical
-Hard Chrome: tested and proven but an involved process

Plating Cylinder Bore Back to Spec., need thick deposit, these are some
metal I thought would be possible: -copper
-nickel
-iron
-zinc
-tin: have heard of pistons being plated with tin for less friction

How big of an engine? What's it for? Will you find joy when it finishes
first in a 1000 mile race, or when it manages to run once on a test stand?

I wouldn't think too hard about plating up a worn bore to save making
myself a piston, unless perhaps it's a miniature engine with a lapped
piston. You're probably better off making at least one part (cylinder
liner or piston) new and fitting everything up.

Consider that if the cylinder is so badly worn, the piston probably is,
too, which means that at the least you'd have to either plate the piston
up to size, too, or you'd have to turn it undersized which would require
that you plate all the more material onto your bore.

Does anyone still hard anodize cylinder bores? I know there was a brief
rage for it around 2000 or so with model airplane engines, but it seems
that everyone doing it went back to hard chrome or nickel.

Keep in mind that anodizing is not a plating process. The surface does
grow, because given the same amount of aluminum, aluminum oxide is bigger
than just aluminum -- but the anodizing penetrates into the parent
material as much as it grows out of it. The anodizing is way hard (it's
basically sapphire), but if it were such a hot-s**t way of doing it, why
isn't it still done by model airplane engine manufacturers?

Hard chrome is -- hard, and low friction.

Nickel is low friction, but I don't know if nickel-phosphorus is; I'd be
interested in how well it stands up (OS engines uses nickel plate on some
of its engines, but I'm not sure if it's nickel phosphorus, and I'm not
sure if it wears super well).

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com