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Homemade Solution - Is sulfuric acid necessary?

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  • Homemade Solution - Is sulfuric acid necessary?

    Hi!
    i am super new to this and am just learning the math, how to make the bath, how to use my rectifier and multimeter etc.
    i am using a 5amp rectifier from amazon, and a bath of copper sulfate and distilled water.
    i was attempting to plate an organic substance.
    The paint I was using was comprised of acetone and powdered graphite lubricant.
    I am switching the acetone to India ink on my next attempt.
    My first attempt was in a 1gal bath. I started as low as possible. 0.01amp and 0.01v copying a youtube video. My rectifier didn't even register a current however there was a noticeable affect. I gradually turned up the amps and current over 48hrs. Topping off at 2amps and 4v at the end.
    Before I began raising the current there was some blue crystals growing on the cathode wire as well as the object was turning blue. Eventually the blue just got thicker but never completely solidified and the cathode wires began corroding.
    I have so far done two attempts and both ended with the copper failing to turn back into a solid.

    It was after my first attempt that I took the surface area into account and decided to try a smaller object and a fresh bath, as there was now a bunch of junk on the bottom of my first bath.

    The second attempt was the same solution of copper sulfate but in a roughly 1L container. With an object with a surface area of about 2inches.
    this time I set the rectifier to 1.2A and 2v for 4 minutes.
    Same acetone paint solution.
    A dark brown rusty layer formed on the wire connecting the object. But a bunch of the paint also came off when I dipped it into the bath. Likely contaminating the bath.
    The rust didn't completely solidify.
    ​​
    I have a few questions that I have found lots of contradictory information about.

    First of all, is it necessary for the bath to contain Sulfuric acid? In the chemistry videos I've watched on electrolysis to study how to do the math, they do not mention the use of sulfuric acid. Only Copper sulfate solution.

    Does a solution without sulfuric acid require a larger amount of amps and volts since it lacks the extra electrolyte?

    What amperage and Voltage do I set my rectifier to in order to copper plate a 2inch surface area in a small vat? (1-2L)

    What amperage and Voltage do I set my rectifier to in order to copper plate an object with a 6inch surface area in a 2-3gallon vat?


    Thanks everyone for any help





  • #2
    Hi Freshcu

    the sulfuric acid is definitely necessary for a good quality copper plating (it is named ACID sulfate copper plating).

    your acid has some important roles. It lowers the pH of your solution, and does not let the copper ions to turn into insoluble hydroxides.
    it also alters the chemistry of the surface, letting the copper ions to reduce to copper metals without oxidation on the surface.

    so you have to ass sulfuric acid to your solution.

    the current and voltage of plating, have nothing to do with the volume of the bath. you can plate in a constant voltage and let the part decide the current, or you can measure the surface of your parts and do the math to calculate the current, and let the voltage get as high as it needs to get. you CAN NOT control both.

    the maximum current density you can use is affected by the concentration of copper sulfate, and the agitation of the bath. you can go around 20-30 ma/cm2 to do it easier.

    I suggest you forget about conductive paint for now, and do some plating with some piece of metal (iron sheet for example). so you become a little more familiar with the whole process. then you can switch to your organic materials.

    p.s.

    I don't know what you are trying to do, but 48 hours for plating is kind of ALOT.
    how thick do you want your coating??
    you can easily plate 1 um/min with acid copper plating bath.
    so if you want to go as thick as 50-60 um, then 1 hour is more than enough.

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