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Chemicals used in tin fusing

Dear Sirs: We are doing an environmental investigation at a site. One small building housed an old plating works in the late 1960s where the described operations were fusing tin and passivating stainless steel. I have info on the SS passivation process, but nothing on the tin fusing. The building wastes reportedly consisted of acids, cleaners, copper solutions, cyanide, and descalers. I presume the copper solutions and cyanide were somehow used in the tin fusing operation. From this sketchy information, can you provide an educated guess as to what copper, cyanide, and other compounds are typically used for tin fusing and a thumbnail description of the likely process? Thank you.

Robert Hammond
- El Dorado Hills, California
2000

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2000

Hi Robert,

The typical part from the late 60's to be tin plated and fused would follow (roughly) these steps.

• Solvent degrease or/and aqueous alkaline soap/soak cleaner, rinse
• Acid dip and rinse
• Cyanide copper plate or strike and rinse
• Tin plate, rinse, dry
• Flux and Fuse by dipping in hot oil
• Remove/clean the flux/oil mix and dry.

The cyanide copper plate is used to insure a clean surface for the tin plate (when you are soldering, you are really soldering to the base metal or in this case the copper plate and not the tin).

• Acids- both processes, HCl or H2SO4 - tin, HNO3 -passivation
• Cleaners - both processes
• copper, cyanide - tin fusing
• descalers - mostly for passivation

Regards,

Fred Mueller, CEF
- Royersford, Pennsylvania

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