Accorind to the table of standard electrode potentials, it is easier to reduce a hydrogen ion than a transition metal ion, such as nickel or zinc. Yet, sources such as the Electrochemistry Encyclopedia for nickel, and here on page 9, for nickel, cobalt and zinc. So, why are the metal ions reduced as oppose to the hydrogen ion?

The standard electrode potentials are for, I believe, 1M solution of the metal compound as a neutral solution in water. The values are not set in stone and change based on pH, concentration, solvent, etc. Plating baths are almost never just a metal salt in water. They have all sorts of additives to get the potential below that of hydrogen and to ensure that the metal adheres properly and with an appropriate surface finish.

i am not completely understanding your ques. Please explore a bit .

UC, this subject interests me quite a bit. Do you know of any links or information sources I could read on the composition of these additites which will help the metal adhere and get the potential below hydrogen?

 

Thanks for the info/help!

Generally, metal plating solutions are acidic and quite a bit more concentrated than 1M. "leveling agents" are the compounds used to help produce coherent, smooth platings. The best ones seem to vary from metal to metal and they are usually organic compounds. I'm sure there's a forum somewhere about this. Plating borders on an art and most of what you'll find are tried and effective "recipes" for plating baths.