Cyanide copper plating

A. Robert,

Sounds to me that you should talk to one of the plating suppliers listed in the Sydney yellow pages and get some first hand professional advice.

The questions you pose would indicate that you know very little about electroplating and the first consideration you must have is the treatment of your waste products and suitable licensing from Sydney Water and the EPA.

Perhaps you might consider using an existing plating company to process your products as there is certain to be someone with capacity already available who has all the knowledge and experience to produce the finish you require.

A. A true shopping list of questions!

1) Rochelle salt is potassium sodium tartrate and is added to a cyanide copper bath as a complexant. It allows for a much lower level of free cyanide to be present in the bath without jeopardising the anodic polarisation. It is also a modest grain refiner.
2) The amount of evaporation will be dependent on the ambient air temperature, the bath temperature, the extraction flow rate and the height of the extraction above the electrolyte level. There are tables available for this from plant manufacturers.
3) Carbon treatment is used to remove any organic contamination that will adversely affect the quality of the electroplating. It should be done with caution as it often results in having to re-add most of your organic additives and re-analyse the bath. It can also be a very dirty job and quite time consuming. There are in-line methods available, but at a price.
4) A nitrogen blanket is not really feasible if you have air extraction. You would need a continuous source of nitrogen gas. However, in theory it should reduce the oxidation of cyanide and it certainly will reduce the amount of carbon dioxide dissolving in the bath.
5) Waste waters must be treated to eliminate all cyanides. You will also probably need to remove any heavy metals. It all depends on your local water authority.
6) Distilled water will be better as it is purer, but it much more expensive. De-ionised water is a good compromise and is the most common solution (sic). Do not use straight mains tap water - you will only cause yourself a lot of trouble.
7) The amount of metal deposited will be dependent on the amount of current passed, the time and to a lesser extent the metal loading of the bath, assuming it is within specification.
8) Typical voltages for barrel plating cyanide copper is about 8-10V. The current will depend on the amount in the barrel, but as a guide, a cathodic current density of 4-6 ASF will be adequate. Multi-barrel loading of a bath will be dependent on the size of the bath and the barrels. Personally I have no knowledge or experience of such a practice.
9) The size of the barrel will be dependent on numerous factors. There is a debate as to whether barrels should be loaded by weight, volume or surface area. It is very much a horses for courses point and should be discussed with the barrel manufacturer. If you are plating plastics, you may need to have an inverted dangler as often such articles float and this too will affect your loading.
10) You will need to analyse the bath every day to determine how fast the carbonate builds up. Once you have determined that, you can adjust your maintenance accordingly.
11) The current and voltage may increase the bath temperature; if it does, look on it as a bonus as you will save on heating costs! You may need to have cooling coils in the tanks.
12)The bath will be useable as soon as it is made up. It depends how fast you can do it and get it checked!
13) Filtration will be needed to remove any unwanted debris that will accumulate in the tank. This could be dust from the atmosphere and extraction, anode sludge, general crap from the plating line etc etc. I would recommend polypropylene filters with a pore size of 1 micron or less. Go for a pump rate of at least 6 tank volumes per hour. In my plating tanks, I usually go for about 10 t-o/hr, but I am involved is specialised plating processes and they are not cyanide copper.

A. HI
ROCHELLE SALT IS SPECIALLY USED FOR COPPER PLATING ON ZINC DIECASTINGS.
AT pH 12.5 IT PREVENTS BLACK COLOR AT HIGH CURRENT DENSITY.
SO YOUR PARTS WOULD NOT BE ATTACKED BY H2SO4 DILUTE SOLUTION BEFORE ACID COPPER PLATING ON ZINC DIECAST.