Rh plating solution

Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

arthur kierski

Well-known member
Joined
Feb 10, 2008
Messages
1,090
Location
são paulo---brazil
i forgot the h2so4 quantity in a rh plating bath----i remenber,that it is 2grams of RH in in a solution of 100cc----i think it is 20 cc of h2so4-------Can someone elucidate my doubt?

Thanks in advance
Arthur Kierski
 
arthur kierski said:
i forgot the h2so4 quantity in a rh plating bath----i remenber,that it is 2grams of RH in in a solution of 100cc----i think it is 20 cc of h2so4-------Can someone elucidate my doubt?

Thanks in advance
Arthur Kierski

Hey, Arthur,

Good to have you back. I, for one, missed you.

It's been about 40 years since I've done any rhodium plating, but, I think those numbers you gave are for 1 liter of solution - 2g/l Rh and 20 ml/l conc. H2SO4. Here's a link that has a little info on it. This is the #1 forum on the internet for plating and other types of metal finishing - painting, powder coatings, conversion coatings, metal coloring, etc. And, lately, Ted added a PM refining category. You don't have to register on this forum and anyone can post.

https://www.finishing.com/304/19.shtml

On there, there's a formula by Goran Budija (see below). He posts a lot on there and has a lot of knowledge. He's very abrupt and never gives any details, but I find most everything he writes is technically correct. I don't really care for the aqua regia part, though. We used to sell a concentrate of 2 g of rhodium sulfate in 100ml sealed bottles. The customer would then dilute it to about 950ml with pure water, add the 20ml of reagent grade 98% H2SO4, and then bring it up to 1000ml with pure water.

At Sel-Rex, about 50 years ago, we sold a lo-stress Rh solution called Rhodex. You could plate a lot thicker than with the 2g/l bath. It was more of an engineering bath. I'm thinking it plated less bright than the standard 2 g/l decorative bath. I think it contained 5g/l Rh, as a sulfate, 50ml/l H2SO4, and some quantity of sulfamic acid that I've forgotten. I think there's a Sel-Rex patent on it. I know there are a lot of "I thinks" in this post, but it has been 50 years.

"Simple rhodium plating bath:
2,5-5 gm rhodium(dissolve it in Aqua regia,then evaporate and add to bath)
20-60 ml sulphuric acid(or phosphoric)
1 lit water ,up to 1 A/dm2, 20 °C temp. platinized titanium anode"

Goran Budija
- Zagreb, Croatia
 
Thanks a lot for your reply Goldsilver pro---whem many years ago i decided to make rh plating bath----i did the folowing way : buy Rh sponge from Kitco or Jm----mix the sponge with 3or 4 times of nahso4 and makes a fussion in a closed kiln for 2,3,hours at 600 or more degress centigrates---let it cool and put in a becker with distilled water and boil it------rhsulphate goes to solution and not dissolved rh---- is filtered and weighted---now one knows how much rh was dissolved----supposed 30grams of rh was dissolved---that is15 rh plating bath,adjust to 1,5litres ,add30 cc of h2so4 before adjusting to 1,5litres-----then put the rh bath in 15 100ml bottles
when is used rh wire, and spent rh baths--the procees to make rh plating solution,requires a thorough purification to eliminates impurities------is tottally diferent

thanks for the moment---i remember now,that i used 20cc of h2so4 per litre -----
 
Back
Top