Summary for nickel plating on aluminum Discussion
Nickel plating on extruded aluminum was discussed as a problem of poor coverage and adhesion in deep or wide-cam features, where nickel does not reach fast enough and aluminum contamination in the zincate and nickel steps causes failures. Jan Malmquist said the shop was using a double zincate with only limited improvement before applying 10 microns of nickel and 10 microns of tin. Robert H. Probert advised a different sequence: use a dilute single zincate, rinse, dip in sodium bicarbonate, rinse, then apply alkaline electroless nickel, followed by final acid electroless nickel or sulfamate electrodeposited nickel, and then tin. Anders Sundman noted that if the first nickel step is electroless nickel, alkaline EN may help better than normal EN because it tolerates more zinc and aluminum, but he also cautioned that the issue may depend on whether the problem appears after make-up or after several MTOs, since EN solutions from different suppliers can vary in plating rate.
Q. We are plating big volumes of cooler in extruded aluminum which have a design like a wide cam where the nickel doesn’t get in fast enough so we solved AL in the zincate and in the nickel and create bad adhesion. we are today using double zincate with a little better results but not good enough. The part shall be plated with 10 microns of Ni and 10 microns of Tin.
Jan Malmquist
plating shop – Huskvarna, Jönlöping, Sweden
2004
? I am not familiar with this idea of going directly from zincating to electrolytic nickel plating, and not being so, I would have expected it to not work. Do you have a history of successfully employing it?
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
2004
 | A. First use a dilute SINGLE zincate, rinse, dip in 4 oz/gal Sodium Bicarbonate, rinse, alkaline electroless nickel (which can stand 100 times as much zinc as acid EN), rinse, then final acid electroless nickel or sulfamate electrodeposited nickel, rinse then tin.
2004 A. Jan, If it allowed to use a copper strike before nickel plating or electroless nickel that’s will helps you with the problem with dissolution of Al and Zn. The problem is the Ph-range in the nickel solution and for nickel to plate fast enough in the low current density. Also the chemistry in the nickel solution can be wrong like the additives both primary and the secondary brighter, chloride concentration, temperature. Regards,
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A. Jan,
You don’t tell us here if you use electroless nickel or electrolytic nickel before. If you use electroless nickel to plate at the first step I don’t believe a alkali EN can helps you if this happens when the EN is new. An alkali EN is better than normal EN to stand more zinc and aluminium. Analyse if your problem’s comes up after some MTO’s if you use a normal EN solution or it happens with every MTO changes. Different electroless nickel solution from different suppliers have variations in the plating rate.
Regards,
Anders Sundman
4th Generation Surface Engineering
Consultant – Arvika,
Sweden
2004
A. You did not give any info as for the pre zincate process. Maybe you have a problem with the cleaner (etching or non etching?) What do you use for desmutting? Do you have fluorides in the desmut? All these parameters are highly important in this process.
Sara Michaeli
Tel-Aviv-Yafo, Israel
2004