Non isulated anodes

What is the problem you are having?

Hello Edwardo,

Can you post some pics of your tank configuration and of the stained and burned parts?� I think if you can do this there are many here who could help you more.

  Tank Inlet.JPG

Hello Dustin, we have no agitation at all, but we filter the bath every two months.

How can I now the correct anode to cathode distance??? The current density is:��±�4 A/dm2�, the bath comp is: cyanide: 70 g/l, caustic: 48 g/l, zinc metal: 26 g/l.

What do you think about�the tank configuration???�

I agree that many cyanide platers do not use bath agitation, but I have seen remarkable improvements in plating speed (via using higher current densities) and bath brightness (for bright copper cyanide baths).� It stands to reason that agitation will help flush away the "spent" solution near the surface of the part and reduce burning in the HCD areas.

You can increase the zinc metal slightly to see if that helps.� Also, where are your carbonates?� 14-25g/L is pretty common and at least 7-10 is required for proper bath performance.� If this is an established bath, I would suspect that you have enough carbonates.� Excessive carbonates cause reduced bath efficiency, which may indirectly cause you to increase current too high, which would burn your parts.

Regarding the spacing of the parts to the anodes, try to make the "flat" of the part facing the anode.� Try to keep the edges away from the anodes.� Edges naturally draw more current and are more easily burned.� You can also try to mask the edges of the parts by using a robber or shield.� It looks like you are using copper wire for racking the parts.� Try to construct a cage of wire near the edges of the part.� It may take some time, but it can help on a trial basis.

Here is the analysis I use for determining carbonates.� It is CRITICAL to rinse many times with step #4.� I usually rinse the filter paper 4 or 5 times.

Sodium Carbonate

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1)� Pipet a 5 ml
sample of the plating bath into a 250 ml beaker.

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2)� Add 50 ml of DI
water to the beaker.

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3)� Set the beaker on
a hot plate and heat to a boil.� Add 20
ml of 10% Barium Chloride while stirring the sample.� Allow the sample to settle.� After the sample has settled add several more
drops of Barium Chloride and observe if any more precipitate is formed.� If so, then add 10 mls more of 10% Barium
chloride.

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4)� Filter the
solution through a #2 Whatman filter paper washing the flask and the
precipitate with hot DI water.

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5)� Remove the filter
paper with the precipitate in tact and place in a 250 ml flask.� Add 100 ml DI water to the flask and place on
a hot plate and bring the sample to a boil.

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6)� When the sample
comes to a boil add 3 - 5 drops of Modified Methyl Orange Indicator to the� flask and titrate the solution with 0.94N
Sulfuric Acid to a permanent purple endpoint.�
Note: Reboil the sample if the color fades to green then continue
titrating with 0.94N sulfuric Acid.

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Calculation:� mls of 0.94N Sulfuric Acid X 1.32 = oz/gal
Sodium Carbonate

oz/gal Sodium Carbonate X 7.5 = grams/liter Sodium Carbonate

Yes,� air agitation can increase carbonate formation.�

Dustin, my chemical suplier is doing the analysis for me, but He ask me about the Modified Methyl Orange Indicator, because he dont now how to make this Reagent.

Thanks!!!

I have a problem with plating evaporators using in refrigerators. I use acid zinc electrolyte. In the middle of evaporators appear roughness (in the area of low current density) which is more noticeable after lacquering. In higher current density surface is smooth. Could somebody explain this? What is reason?