1. Plating Rectifier Rated Voltage
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When the pole spacing of the plating tank and the anode area are fixed, the current density of the plated workpiece is generally proportional to the applied voltage. If the voltage is insufficient, the current density is low. Therefore, the upper limit of the DC voltage required by the plating tank must meet the maximum working current of the plating tank required by the highest current density.
Voltage adjustment range: the upper limit value should be equal to the upper voltage limit of the plating tank plus the voltage drop of the busbar: the lower limit value should be equal to the lower voltage limit of the plating tank and the voltage drop of the busbar. In actual production, a rectifier with a larger voltage adjustment range is often selected to meet the needs of different process configuration changes.
However, when the actual working voltage is much different from the rated voltage of the rectifier, it will seriously reduce the efficiency of the rectifier and cause waste of electric energy. In particular, the capacity of electroplated rectifiers is generally big, so the waste of electrical energy cannot be ignored.
In addition, for the thyristor rectifier, when the actual operating voltage is much different from the rated output voltage, not only the efficiency is low, but also the output DC current fluctuation becomes bigger, in some cases it may affect the plating quality, so in the process under stable conditions, a slightly higher voltage of the rectifier is necessary, but it should not be too much different.
According to the rectifier equipment standard for electroplating, the voltage regulation range of the rectifier can be continuously adjusted at 30% of the rated voltage, and ensure that at 66% and above of the rated voltage, it should be able to continuously operate at 100% of the rated DC current and at the rated voltage When operating below 66%, it must be able to carry at least 50% of the rated output current. For example, the resistance of the nickel plating solution is small, and the current required by the process can be reached with a very low voltage. Therefore, when selecting a nickel-plated rectifier, the actual required tank voltage is 3 ~ 4V. Considering the DC bus voltage drop and other factors, choose 6V The rectifier is suitable. When the voltage is adjusted to 4V in production, the load rate is 66%, and the current waveform can also be within the smooth range: if you choose a 12V rectifier, you will not get a smooth waveform, and you will not get a dense and smooth Nickel plating.
2. Plating Rectifier Rated Current
The rated current of the rectifier should be equal to or slightly larger than the maximum working current of the plating tank, which can be calculated by the following formula:
Ic≥DKSmax
In the formula IC-Rectifier rated current, A;
DK-Cell current density, A/dm2
Smax-Total area of workpieces in the plating tank, dm2。
Considering that the un-insulated parts of the hanger will also consume current, when the workpiece are more complicated, a larger current will be concentrated at the corners. Therefore, in order to ensure that the workpiece can reach the current density required by the plating process, the total area of the workpieces should be increased by 5% when calculating the rated current of the rectifier. Therefore, when selecting the rectifier, it is not necessary to increase too much additional value of the current, which not only saves energy but also saves investment.
3. DC voltage and current density required for different plating
Table 1 DC voltage and current density required for different plating
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Q. From the literature, I found that the optimum condition for my nickel electroplating is as follow:
electrolyte concentration: 100 g/L of 450 ml NiSO4
Temperature : 60 °C
pH : 4
Boric acid : 20 g/L
However, while I was running my experiment at 15 Volts for the plating, the temperature was increased 30 °C for every 10 minutes. So after 20 minutes, the temperature of electrolyte was increased until 90 C. My question is how do I control the temperature to carry on my experiment and the deposition for my thick nickel plating will not be affected?
I wish to plate a thick nickel 'nugget' from my experiment. please share your experience.
Thanks.
Haf_Ang
Chemist - Malaysia
A. 15 volts is mega too high for nickel plating. Drop the voltage to 4 V for a start and use a lot longer time. High amperage nickel plating requires extreme agitation.
You might try putting your anode a little bit closer to the part (cathode). For beaker plating, you could go to 1 inch apart for many things.
Set your beaker in a large glass dish that is about as deep as the liquid level of the beaker and add an inch of crushed ice to the dish. Add more as the temperature rises.
You can agitate your solution with air from a fish tank air pump.You will need a control valve in the line. Do not use a fish tank air rock as the solution will dissolve it. You can put holes in the plastic tubing on the bottom of the tank with a drill or a red hot paper clip. Weigh the tube down with a glass rod or stainless steel wire.
James Watts
- Navarre, Florida
Q. Thanks, Mr James Watts. But now I meet a problem that instead of using 15 Volts, 4 volts electroplating take much longer time to get the plating. So I hope to maintain the high deposition rate and its temperature as well.
I'm thinking whether I put the anode and cathode too close that generates high temperature to the system, the distance between the electrode is about 6 cm far away. Is the distance a factor for temperature raising?
Mr James, about your suggestion of agitation of air, the temperature will not go up so fast, but after a period the temperature will still increase slowly. How do I maintain the temperature at only 60 °C? it really a big problem to me.
And also, I found that the Stainless steel anode that I used will pollute my electrolyte to produce my nickel plating because the dissolution of the SST will dissolve it high content of iron into the electrolyte. And if I use the nickel as anode the dissolution rate will be faster than the SST anode, and I found that it is not cost effective to my nickel plating. So do you have any ideas about what kind of the anode used in my experiment, that is low dissolution and high oxygen evolving? Thanks//
Haf_Ang
[returning]
Chemist - Malaysia
byon AbeBooks or Amazon
A. Everyone wants to plate faster, Haf, but they'd also like cars that go 200 MPH, get 100 MPG, and carry a family of 7 in comfort. A starting point is to compare your current density with published values. You probably will not successfully plate at much over 40 amps/ft2. Where are you now?
The closer the anode to cathode spacing, the lower the voltage; and the lower the voltage, the lower the temperature rise. But you certainly need nickel anodes, cost effective or not. It is hard for us to guess what we need to tell you about if we don't know what you know and what you don't. That's an advantage of books: there's enough room to cover everything. Do you have access to a few books on nickel plating? Good luck.
Ted Mooney
, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
If you want to learn more, please visit our website Gold Plating Machine For Sale.
Q. Mr Mooney, my knowledge of electroplating is all from self learning, basic chemistry knowledge, and some literatures from internet. So I need some professional ideas to get my electroplating successful. Or if Mr Mooney can suggest any books/websites that related to my experiment, please kindly share with me. Thanks in advance.
By the way, I have a question regarding to the spacing between the electrodes and temperature. I previously thought that the closer the spacing, the higher the temperature, because while the distance between the electrode closer, the conductivity will be increased, and it generates the heat, thus temperature raise. However (if I did not misunderstand), Mr Mooney do you mean that if the spacing between the electrodes closer, the voltage will be lower and also temperature become low? is totally opposite to what I assume.. Then my assumption was going to the wrong way?
Actually, the main purpose of my experiment is to plate the nickel out from the electrolyte as much as possible, and not kind of decorative plating. So, is it really necessary to use nickel as anode? because I will gain the plating yield from the dissolution of the anode, the extraction from the electrolyte is meaningless then..
Haf_Ang
[returning]
Chemist - Malaysia
A. Sorry, but after 3 postings and 3 responses I still don't quite understand what you are trying to do or why, Haf. But the closer the anodes to the cathodes, the lower the solution resistance, so the lower the voltage you can use, so the less power you waste to the solution and lower the heating effect.
As for other websites to visit, please google for Ohm's Law. After you feel comfortable with that, google for Faraday's Law. Those will arm you with the basic understandings you will need to understand the relationships between voltage, current, spacing, plating time, thickness of deposit, etc. For books, any of the "must have" texts on our Books page will be tremendously helpful.
You will find it impossible to plate nickel to low levels this way though. The "efficiency" will drop faster than the nickel concentration. That is, as the nickel level drops, more and more of the applied electricity will just release hydrogen and oxygen instead of depositing nickel. To recover nickel from waste, you generally need super large surface area cathodes (reticulated copper or carbon) and extreme agitation. Good luck.
Ted Mooney
, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hi, I had been advised by Mr Mooney that >40 A/ft square won't give successfully plating, so I control my current density below 35 A/ft square with the space of inter-electrode of 2.5 cm. But the plating efficiency is not good in my 20 A current experiment. So I m wondering whether inter-electrode distance is too close resulting in depleted metal surrounding the cathode or the current density is too high for good plating efficiency? Or any information about relation between the electrode gap and the current density?
Haf_Ang
[returning]
Chemist - Malaysia
A. Hello again, Haf.
You will need a platinized titanium anode if you will not be using nickel anodes. There is certainly a relationship between solution agitation, interelectrode distance, solution concentration, and maximum successful current density -- but it isn't a simple formula. Each of those variables interacts with the others.
Your close interelectrode spacing helps keep solution resistance down, which directly keeps plating voltage down, which directly keeps power consumption down -- and power consumption is the same thing as heat. So you do not want to increase the distance, you want to increase the solution agitation!
In your first posting you said your object was to make a nickel nugget as an experiment. When we advised what parameters to use, you said plating that way would be too slow and nickel anodes are too expensive, which didn't seem to make sense if you were trying to make a nugget. But when we tried to clarify the issues in that new light, you then said the answer was no good because your object was actually to remove the nickel from the solution. Then we said that will not work properly with this setup because the efficiency will plummet as the concentration goes down. Now you are saying the efficiency is too low.
Can you please help by forthrightly describe exactly what your goal is -- what exactly you are trying to do and why? In other words, are you a student trying to make one nugget, or are you an engineer trying to build an electrowinning plant for the production of nickel, or are you trying to develop a process to remove nickel from waste streams as a pollution control measure, or what? As you can see, we can't efficiently help you get where you trying to go if you don't tell us where you're trying to go :-)
Thanks!
Ted Mooney
, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
byfrom AbeBooks or eBay or Amazon
Q. I have a question regarding Nickel electroplating. I am a student at a university and I'm planning to work on a thesis that would recover pure Nickel metal from a Ni-Cd battery through electroplating. The battery would be dissolved in sulfuric acid. The electrolyte would contain Ni, Cd, Fe, Co, Zn and other metal ions. Using stainless steel as cathode and Pb as anode, do you think it would be possible to electro-deposit pure Nickel alone under a specific current density?
What do you think are the conditions that could produce such result? Your response on this matter would be highly appreciated.
Paolo Pulido
- Diliman, Quezon City, Philippines
A. Hi, Paulo. No, I don't think you can recover pure nickel that simply. But you may be able to precipitate the iron with peroxide, dummy out some of the other metals, or precipitate them out. Nickel-cobalt is a plateable alloy, so I'm not confident that you will be able to plate one preferentially.
Regards,
Ted Mooney
, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hi,
I need to electrowin nickel from sulphate solution, prepared by dissolving nickel carbonate in sulfuric acid. Solution does not contain any impurities other than chromium and copper below 100 ppm. Nickel concentration in solution nearly 60 to 80 gpl but I have to go down to 15 gpl. pH 3.3 to 3.5 by NaOH.
I need to know what is ideal amps to be applied at anode and volts at electrode to deposit nickel. Any recommendations for operating parameters shall be of help.
Regards
K. S. Shah
- Mumbai, Maharashtra, India
A. Raise the temperature to 140 °F, and plate at 20 ASF, or higher current density if well agitated. Additives are not needed, but sodium lauryl sulphate might be helpful to reduce pitting.
Lyle Kirman
consultant - Cleveland, Ohio USA
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