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Corrosion Resistant surface inside a complex bored hole through aluminum

(-----) 2006

How do I get a corrosion resistant finish on the inside surface of small (water carrying) holes bored through aluminum. (depths up to 2", diameters down to 1/8")

Most electroplating techniques do not 'carry' far into the bores.
Non electroplating techniques can leave pin holes and larger unplated areas due to undisturbed air bubbles in the bores.

Does anyone do a process where the plating solution is pumped through the bores?

It would have to be simple as this is a 10,000 to 20,000 parts per annum requirement.

Michael Draper
electro optics - Taunton, Somerset UK


I believe that a selective plating process will be suitable for this application, but there are only a few companies able to supply this. Sorry I couldn't be more specific.

Mark Smith
- Worcester, England

First of two simultaneous responses -- 2006

From my experience with brush plating, I do not think that it is practical to try to brush plate 10,000 to 20,000 parts with holes that go down to 1/8" Dia.
If the part was steel, I would think that EN with heavy air agitation could work by a very good EN plating company. On aluminum, it only stands half the probability, because of the additional zincating steps.
If the holes were thru holes and only went from top to bottom, there is a possibility that they could be electrolytically plated by a very good plater. It would require some great fixturing.

James Watts
- Navarre, Florida

Second of two simultaneous responses -- 2006

Aluminum is anodic to most plated metals, so its eventual galvanic corrosion is inevitable.
If this is a closed loop cooling system (or can be converted to one), add an anti-corrosive to the water. E.g., automotive coolant.

Ken Vlach [dec]
- Goleta, California

contributor of the year Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.


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