Summary for lead plating alternatives Discussion
Alternatives to lead plating for a copper washer used in a metal-to-metal seal were discussed for a cryogenic and steam application. Singh Surinderpal Singh said the lead-plated washer is squeezed under a nut so the soft plating deforms and prevents the copper base from being exposed. He reported that pure tin failed and leaked at low temperatures, indium worked but was too expensive, and a 60% tin / 40% bismuth plating performed as well as lead. The thread does not show a definitive universal replacement, but it suggests that soft, deformable plating systems are the key requirement and that the tin-bismuth combination may be a practical lead-free option for this specific use. Because the application is demanding, any substitute would need to be validated under the same cryogenic and steam conditions before adoption.
May 13, 2011
Q. Hello,
I am trying to get away from Lead(Pb) plating because of cost and RoHS.
It is a washer made out of Copper and plated with Lead (Pb). This washer get squeezed under a nut between two surfaces. While Copper get squeezed, along with lead (Pb) get squeezed too, which avoids copper (base material) exposure. This is a metal to metal seal.
I tried 100% Tin (Sn) plating but it failed and leaked at low temperatures. I tried Indium and it works but very expensive. I tried very odd combination 60% (Sn) and 40% (Bismuth) plating. it worked as good as Lead (Pb) plating. Application is cryogenic and steam.
Do you know any other alternatives or other combinations. Please help
Regards
Singh
Surinderpal Singh
Product designer – Lincoln Park, New Jersey, USA
Q. I am trying to get away from Lead(Pb) plating because of cost and RoHS.
It is a washer(about 1″ dia) made out of Copper (base meterial) and plated with Lead (Pb). This washer get squeezed under a nut between two surfaces. While Copper get squeezed, lead (Pb) plating get squeezed too along with, which avoids copper (base material) exposure to mediam This is a metal to metal seal.
I tried 100% Tin (Sn) plating but it failed and leaked at low temperatures. I tried Indium and it works but very expensive. I tried very odd combination 60% (Sn) and 40% (Bismuth) plating. it worked as good as Lead (Pb) plating. Application is cryogenic and steam.
Do you know any other alternatives or other combinations. Please help
Regards
Singh
Surinderpal Singh
– Lincoln Park, New Jersey, USA
August 26, 2013