Letter 20083

Nickel Hydroxide [Florida] 

+++

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, FL, USA

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

James Watts
- FL

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 Inc. - Brick, NJ

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
- FL

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, NC, USA Editor's note:        Mr. Probert is the    author of Aluminum How-To

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

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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