Bismuth-tin solder replacement causing steel scrap contamination

Lead-free solder researchers proposing bismuth-tin alloy; Tom's objection at conferences that putting bismuth into automobiles would destroy steel recyclability (bismuth segregates to grain boundaries, embrittles). "Dead on arrival" — the solder metallurgists didn't know steel-making.

Fifteen years ago people were trying to get lead out of solder, and they're still trying to get lead out of solder. I'd go to these conferences and they'd say, we've developed this bismuth alloy. I said that's great — so you're going to start putting pounds of bismuth in every automobile, which means we will no longer be able to recycle steel automobiles. That was dead on arrival, but these metallurgists working on solder didn't know anything about steel making. They didn't realize nobody was going to put bismuth alloys into the soldering on an automobile, because you can't — you'd have to separate the scrap. You can't just shred up the automobile and dump it into the furnace, you'd have to separate it out. We do separate some things — we take out the airbag explosive, because that has killed people in the steel mills when they're shredding and all of a sudden a piece of shrapnel goes through someone's arm. They do some things, but you can't start ripping all the wires out — you couldn't afford to recycle the steel.

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The $100M/year US research program on tin-bismuth as a lead-free solder replacement, which Tom argues was systems-blind because bismuth segregates to steel grain boundaries during automotive recycling and cannot be oxidized out.

A lot of people, when they first started looking for lead-free solders, looked at bismuth alloys. There was a hundred million dollars a year being spent on coming up with tin-bismuth primarily. Bismuth was cheaper than lead. Does anyone have any idea why a choice of bismuth-tin would be such a terrible choice? Because it would destroy the recyclability of a billion tons of steel each year. You can get lead out of steel — you can oxidize it out when you remelt the steel. You cannot get bismuth out of steel. Bismuth goes to the grain boundaries of the steel. Where does the largest single fraction — not the majority, actually probably the largest single fraction — of steel recycling come from? Automobiles. And there are electrical solder joints in automobiles. These people wanted to get the lead out of automobiles. They've never replaced the lead acid battery — that's another thing we can talk about. We're still using lead acid batteries, but that's sort of localized; you can unbolt it and send it to the battery recycling center. But solder joints, they're all through the car. You're going to have someone go in there and take out all the solder joints in a car before you try to recycle it? It would cost a fortune to recycle.