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electro cleaning before electroplating

Hi.
I made the instructable of A_Steingrube"high quality and safe nickel plating" address:https://www.instructables.com/id/High-Quality-and-safe-Nickel-Plating/
and i want to be sure that i did the elctro-cleanning that is mention on step 4 correctly.
I try to ask A_Steingrube through the comment place and the private message but i have not get any answer yet.so i try to ask here.
I made the elctro cleaning while my object was connected to the positive voltage and the wire connected to the negative voltage.I did that ,because i understand that the object sould be dissolved abit and this should be happens on the anode(connected to the positive voltage) but in step 4 he mention to connect the object to the negative voltage in order to make the electrocleanning.SO,is there something that i miss here?
Thanks in advance.

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caitlinsdad3 years ago

From what I am understanding, electrocleaning is an extra step you do before the electroplating in order to remove any remaining oxidation on the object. The process is to hook up the object to be cleaned to the negative voltage. A bare wire is attached to the positive voltage. That wire and the object are then placed in the solution for a few seconds. Because the positive voltage lead is not attached to a piece of nickel, the electrochemical reaction is to draw away or remove the oxidized molecules from your object instead of depositing a new metal.

xchcui (author)  caitlinsdad3 years ago

Hi caitlinsdad.

I don't understand why my object should not be connected to the positive voltage.

I have been told that when i make electro plating,the object that you connect to positive voltage that is acting as the anode is dissolved into the solution and the object that connected to the negative voltage that acting as the cathode is plated with the metal that was dissolved from the anode.

So here when i connect my object(cathode) to the negative voltage in order to do electro clean ,it seems that the object will be plated with the metal that the wire is made of,because the wire is acting as the anode and it will be dissolved.

So in order to remove any remaining oxidation from the object,the object should be dissolved in the solution a bit,shouldn't it?

Doesn't it happens when it is acting as the anode?connecting to the positive voltage?

I think you have to look more into the chemistry. My guess is that copper oxide, the dirt, is more attracted to the positive charge so it will pull off of the cathode and be drawn to plate the bare positive charged wire. You have to see how the ions or molecules act in solution.

xchcui (author)  caitlinsdad3 years ago

Thanks for your replies,caitlinsdad:)

Before i did this electro plating i asked the members of the forum some question a bout the process and it took me awhile until i understood all the movement of the ions and what is the chemical process that happens when the electro plating is happened.I understood from it that in order to plate an object we need ALWAYS to connect it to the negative voltage and the object that connects to the positive voltage ALWAYS dissolved into the solution and drawn to plate the cathode.

Until now i was sure that i understood the theory of this but now i am very confused.

Now i see from your explanation that at this situation(electro-cleaning) it is totally opposite-the cathode is dissolved and the anode becomes plated.

How come?

When you says"my guess..."do you mean that you are not sure about that?

because from all the instructable this is the last issue that i have not understood,yet and i want to be sure that this is the right answer.

I am not a metallurgist or electrochemical engineer, I only recall things I learned in high school. That said, the word electrocleaning is used to describe a process to remove oxidized metal from the penny. The oxidized metal/tarnish/dirt is most likely copper oxide, I would have to look it up what the molecule is but most likely a chemical compound of copper and oxygen atoms and maybe something else it pulled from the air. When put in water, those molecules can float and turn into charged ions, get a negative charge or positive charge based on the atomic structure/free electrons of the copper/cupric oxide, whatever the oxidized molecule is. The battery current provides the big attraction for those loose ions which is greater than what it can hold itself together with. Because of the oxidized molecule ion's structure which is dissolved in water, it is looking for more electrons to make it more stable, it is attracted to the positive wire in the water. Your understanding of electroplating might just be restricted to what to do with a pure metal. Anodizing aluminum or chrome plating plastic parts would be other processes that use the same idea for electroplating but might turn out to what we understand as electrocleaning.

Oh, experiment. You already overcame the fear of electrocution or exploding things, so...

The other thing is it might just be electrolysis to get rid of the oxygen atoms bonded to the copper which results in oxygen bubbles at the positive terminal and a brighter unoxidized copper.

xchcui (author)  caitlinsdad3 years ago

I just thought that i understand the subject and after your explanation,i find out that this is more complicate than what i thought.

So what is actually happens during the electro cleaning in the vinegar+salt solution?while the copper object is the negative and the wire is the positive.

I understand that the oxygen atom leaves the object while hydrogen bubbles create at the cathode and oxygen bubbles create in the wire.So does the wire(anode)become copper oxide after the electrolysis?does the wire dissolved into the solution(get eaten)?Does my object,besides of be unoxidized,also increase its weight by attract copper ions that maybe dissolved from the wire?

All of that would be a good topic for a basic science experiment. With a good scale you can observe all the changes and predict or confirm the chemical reactions. Have you taken any courses in chemistry in school?

xchcui (author)  caitlinsdad3 years ago

Yes,i have basic knowledge at chemistry,but i was not deep in it then.

I am not doing experiments,i just plate something as A_Steingrube shows in his instructable.I did the nickel plating i understand what happens in the solution and what happens with all the ions that in the solution and there movments.Also i could see that the nickel anode was eaten and the bubble around it while the cathode was plated.i got full explanation,really big and professional explanation a bout what happened there.

And when i did the elctro cleaning while i connect the object to the positive voltage and i saw(at A_Steingrube instructable)that it should be connected to the negative voltage and i wondered why?maybe it is mistake?and if it is not mistake what happened exactly in the solution with the object an the wire?

I hope you can answer my question as i wrote on the last post.

I only want to understand the specific process which happens at this specific elctro cleaning.

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