Letter 40096

Nickel plating is flaking  

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We have a process that we dip a rotating basket with brass pieces in a solution tank. Attached to the tank is a anode and cathode with a 9vdc running at 90amps. Our parts seemed to be getting a double plating and is flaking. Have any ideas what we can look at?

Thanks,

Paul Porter,Jr.
healthcare - Deland, FL, U.S.A.

Are the parts "leaded brass" ? If so you require special service preparation. Clean-rinse-50%Fluoboric Acid -rinse -optional fluoboric acid copper plate -rinse - nickel plate.

The lead forms an insoluble in the regular acid dips normally used for plain brass (sulfuric or hydrochloric). The lead does not form an insoluble with fluoboric acid. So the acid dip change alone may help. However, the lead could also form an insoluble before it got plated in the slow plating barrel. When nickel plate bridges lead oxide - it peels. Ideally, you would first strike in fluoboric acid copper and then your nickel solution would not "see" lead because it would be covered by bonded copper.

Robert H Probert Robert H Probert Technical Services Garner, North Carolina Editor's note:        Mr. Probert is the    author of Aluminum How-To / Aluminio El Como

You give very little information about your process or conditions, so anyone answering is shooting in the dark. Firstly, wha is the surface area of your parts; secondly, what type of nickel are you trying to electrodeposit; thirdly what are your conditions; fourthly what pretreatments are you using; fifthly, what is the brass substrate? Taking the caveat that we haven't a clue about your process, I can only suggest the following. 1) You have an intermittant cathodic connection resulting in a break in current and subsequent delaimation of the nickel; 2) do a Hull cell test to make sure the nickel bath is behaving corectly; 3)ensure the plating bath is in spec as far as temperature, pH etc is concerned; 4) ensure your cleaning procedure is correct and in spec; 5)make sure your brass is not leaded - if it is you will see black streakes underneath the peeling nickel and on the brass.

Trevor Crichton R&D practical scientist - UK