The authoritative public forum
  for Metal Finishing since 1989
-----

Acid copper plating is blistering

I run a small antique automobile restoration shop. I typically do all of the metal finishing buffing in my shop then turn over the parts to the plater for processing. I have a early steel radiator shell that was very rust pitted. I sand blasted it then got it stripped. I ground off as much metal as I dared then had the shop apply a heavy copper. This was repeated a second time. Since I ground through the copper to the base metal it needed a third and lighter copper. When doing the final buffing, the heat of the buffing wheel caused the copper to blister in one area. The plating shop says you just can't put on multiple layers on copper and expect good adhesion. Is he right or do you suspect contamination of some sort.

Curt Schulze
Automotive restoration shop - Prescott , Wisconsin, USA
2004

---

I agree to some extent with your plater that several layers of plating will tend to not promote good adhesion. I say this because every subsequent layer is a potential source of poor adhesion. Your adhesion is only as good as your least effective activation process. What you are attempting to do is not uncommon, but it is uncommon for someone not to do the polishing, buffing and plating all under one roof. I know I sure wouldn't try it. I'd want control over the entire process. Daryl Spindler, CEF decorative nickel-chrome plating - Greenbrier, Tennessee 2004 You could have a couple of different problems here. If you are grinding down to steel in spots and copper in other areas they need to apply a nickel strike to re-initiate the plating process. If you do not apply a nickel or cyanide copper strike the acid copper will form a non-adherent immersion copper plate. Subsequent layers of plating will not have good adhesion and the heating process of buffing will only exacerbate that problem. If a plate is done correctly you will have to chisel it off the part. Most likely what happened is that the part was not cleaned or activated properly at some point. If heat from a buffing process is applied to that area it will blister. All you can do now is to sand down to good metal and have the plater replate the part. Start out with 280 grit and work up to 400 grit. How long is the plater running the part in the acid copper? You could also ask the plater to put on a nickel plate so you can see when you sand through the copper. Tom Haltmeyer - Peoria, Arizona 2004 Curt: 2004 If the copper bath is heavily loaded with organics, there could be an adhesion problem, but if it is a simple copper bath, there shouldn't be any problem as long as the surface is properly prepared. All contamination, such as oils, greases and oxides (rusts) must be removed and the surface kept as clean as possible prior to plating. There are numerous tricks electroplaters use to improve the adhesion, so your plater should know them. Trevor Crichton R&D practical scientist Chesham, Bucks, UK

---

2004

Curt,

The blisters your experiencing are purely down to poor preparation prior to plating, plating copper on copper requires very thorough prep. So your choices are : you grind/polish out blistered area , and then chuck it back at your platers , or locally build up the damaged area using a brush plating process ... i.e. Sifco, etc.

Good luck bud,

Garry Williams
- Lancashire, England

---

2004

Trevor:

Could you list some of the tricks that are used to help with adhesion? One I do is to sandblast with silica sand. It gives more of a mechanical grip for the next plate.

Thanks,

Tom Haltmeyer
- Peoria, Arizona

---

A thorough soak and electrocleaning followed by a bright dip is, in my experience, the best pretreatment for acid sulphate copper over copper. Obviously, if thickness and other factors for the particular case allow it. Also, ramping up the current will help a lot.

Guillermo Marrufo
Monterrey, NL, Mexico
2004

---

Plating copper on copper is very basic and yes plating works. Now plating Acid copper over directly over exposed steel would be cause for an adhesion failure. Copper lifting from copper is a PLATING defect. Either the product was not properly cleaned, an oxide may have been left the part, or the wrong electrolyte (acid vs cyanide)was used. Electroplating were bonding atoms of material this can only be accomplished with a medically clean surface.

Rick McCarthy
- Chicago, Illinois, USA
2004

Curt,