Where the
world gathers for metal finishing
Q&As since 1989




-----

Top layer coatings for pewter watches

Hi, we have introduced some fashion watches to the market and these are not very high graded with top metals. this was made out of Stainless steel and pewter. Some of the cases surrounding the dial got discolored quite easily and we did a clear lacquer (E coating) on top.

But from that even it did not survive, we want to give a guarantee on the discoloration at least for one year, and we are having a horologist too, to remove the movements and to do any sort of a re assembling. If you have any remedy such as a coating system that will survive the top layer for one year please let me know -- remember that we are so close to the equator and whatever the coating system should be a good one that will not react to sweat too.

Tharanga Jayawardena
Fashion jeweller - Colombo, Sri Lanka
December 16, 2010

---

In India the watches are coated with a combination titanium nitride and gold by PVD processes and it is popularly known as ion plating. In the past I have coated stainless steel cases and straps by vacuum arc and sputtering techniques. I suppose even in Srilanka the coatings may not seriously discolour over one year.However the luster of the top layer of gold would not last. But that is not noticed by the user. If you are not particular about gold colour, other PVD coatings are possible.

I understand that pewter is an alloy of tin, lead etc with low melting point. Coating this material may be tricky as these substances are likely to contaminate the coating machine. One also has to consider the compatibility of the substrates and the coating for proper adhesion and expected finish.

H.R. Prabhakara - Consultant
Bangalore Plasmatek - Bangalore Karnataka India
December 19, 2010

---

December 21, 2010

Dear Prabhakara.

Thanks a lot for the reply.Any way its quite difficult to do the iron plating for the pewter. As you are aware pewter is having a a very low melting point

Pewter is a soft, highly malleable metal alloy. Tin comprises the base metal (between 85 and 99 percent), with the remainder consisting of copper (as a hardener) and another metal (usually antimony or bismuth in modern pewter). metals, pewter has a melting point of 225 to 240 °C (437 to 464 degrees F). Iron plating is quite alright with stainless steel as you have mentioned but not in pewter.

Still waiting to see a proper remedy for the watches top coating, anyway I appreciate your reply.

Tharanga Jayawardena
Fashion jeweler - Colombo, Sri Lanka