Coating Process (Palladium/Ruthenium Alloy)

A. The part can be done by several of the methods you mentioned, but the big question would be what is the price target, how thick does the coating need to be, and what is the uniformity spec for the inside length?

Electroless for these metals would work, even in a barrel, but the inside would not be as uniform as as the outside. Barrel electroless would offer cheap labor & capital equipment per part, but low plating rate, expensive chemistries, and would require a relaxed uniformity spec on the inside. The low plating rate can be offset by large lot size in a barrel. Another electroless method that may lend better uniformity is to stand them all in a batch on end on a vibrating screen and pump the electroless up through the screen where it overflows back into the reservoir.

Electroplating would give high plating rates/part and superior uniformity on the inside but would require a higher capital equipment investment as each part would be placed over an electrode for the plating step while solution is being pumped through it. There are many more such tricks.

Hope it helps,