Letter 20083

Nickel Hydroxide

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If you don't have NaOH in the tank where the Nickel hydroxide is forming from? My tank is nickel sulfamate tank.......

Franklin Gutierrez
Goodrich - Miami, Florida

First of two simultaneous responses -- +++

This letter might have been meant to be attached to another one and it is not. What are you talking about??

James Watts
- Navarre, Florida

Second of two simultaneous responses -- +++

Nickel plating is efficient but not 100 percent efficient; some of the electricity seperates water into H+ and OH-. The H+ evolves as hydrogen gas, leaving behind the OH-. In fact, that is why boric acid is frequently added to nickel tanks--to help buffer the pH against this buildup of OH-.

Ted Mooney, P.E.
finishing.com
Brick, New Jersey

First of two simultaneous responses -- +++

A supplement to Teds comment. The boric is there mostly to buffer the OH buildup in the barrier layer which is the ultra thin layer of solution touching the part. This keeps the plate from turning dark.The overall compensation for the pH is the addition of sulfamic acid which is typically at least weekly.

James Watts
- Navarre, Florida

Second of two simultaneous responses -- +++

If for any external reason the pH in the Sulfamate Nickel Solution gets up around 5.5 or 6.0, the Nickel will form the Hydroxide from the OH in the water.The solution will turn a lighter shade of green color and start to floc out as a light green sludge.

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

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Nickel sulfamate anode bags show a green slime contaminant, my guess is an inorganic contamination of some sort.. mainly I guess nickel hydroxide, if the tank does not contain any hydroxide how is it formed? and is that green stuff something else????? what is it?!?!?

Franklin Gutierrez
- Miami, Florida, USA

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There is always some hydroxyl ion present in an aqueous solution unless the pH is so low that it cannot be measured with a normal pH meter. Your guess that the green slime is nickel hydroxide is a good one, although at normal plating bath pH, the growth should be slow.

Don Piett
- Thompson, Manitoba, Canada

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