The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Flaking of Gold Plated Aluminium

2002

My boss is installing gates that have aluminum spear heads on the top. He has had them gold dipped, clear dipped, buffed and polished in order to stay shiny in all weather. The gold is flaking off.

Can you tell me if there is a specific way to do this to stop the flaking?

Thanks for any help you can offer,

Trish Bradshaw
- Perth, Western Australia, Australia

---

I don't know what "gold dipped" means. Dipped in molten gold? Dipped in gold paint? Electroplated? Gold leafed? If they were electroplated (and electroplated right) the gold will not come off.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002

If dipped means plated, allow the plater one more try and then find another plater. Improper cleaning and zincate steps are the most probable but far from the only possibilities.

James Watts
- Navarre, Florida
2002

---

All of the above is good comment.

If the aluminum is really gold electroplated, then what is between the aluminum and the gold It must be nickel or platinum or rhodium or cobalt. The zincate from the aluminum preparation will march (migrate) right up through the gold unless some sort of diffusion barrier is there.

If you just have copper between the zincate and the gold then in time the zinc, copper, and gold will migrate into each other.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2002

---

2002

To further clarify our dilemma:

1. Cast aluminium spear points for gates were used
2. To our knowledge, the spear points were not treated prior to being dipped in molten gold.
3. It was then coated with a clear plastic coating.
4. Within 2 weeks white powdery blisters developed under the gold and the clear plastic coating blistered.

Is there a treatment to the aluminium that can be done prior to the gold being dipped to prevent this or should another metal be used?

After the gold is buffed, is there a particular kind of all weather coating which should be used? Thanks for any help you can offer.

Trish Bradshaw
- Perth, Western Australia, Australia

---

The gold has to adhere by itself, not by being shrink-wrapped into place by a topcoat. A better process would be (I think): zincate, electroless nickel plate, gold electroplate. The topcoat is only to keep the gold from wearing away, not to keep it from flaking off, so an alternative to a clearcoat would be to titanium nitride it (this will protect the gold and is very close in color to the gold).

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002

---

Here I am again. Ted's message above is the last word.

However, go look at my answer to Kevin Nash above on letter number 16869.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2002