[function_seven]

There are these world-changing inventions we look back on and marvel at. The Haber–Bosch process, the Bessemer process, rubber vulcanization, etc.

My dream is one for stainless steel. Come up with either a different alloy or an improved process to make corrosion-proof metal from abundant iron. I can't imagine the leap forward if a chunk of stainless cost nearly the same as mild steel. (And didn't have weird failure modes, etc.)

[eternityforest]

For some applications, plastic fills that role very well. A lot of stuff would probably be made with plastic, and be just as durable, if we didn't have this "Stuff should feel substantial" design mindset.

It's amazing how there's such a strong preference for things with size and weight, and how plastic is seen as cheap trash rather than an engineering marvel.

[function_seven]

I have a hand cart / furniture dolly that's almost entirely plastic. The only metal bits on it are the axle and the handle. It's perfectly durable and I've used it to cart around items that weigh 600 lbs. (300kg).

It's also a good little example of where plastic is good and where it's not. The axle and the handle get the largest amount of stress, so they remain steel, while the body of the cart can be a trussed plastic mold to achieve the strength needed.

Portable gas cans are another area where plastic wins in my book. It's lighter, more impact resistant, and cheaper to mass produce. And it don't rust! Sure, there are probably niche cases where you want a metal jerry can, but for most applications a blow-molded plastic container is better even if it wasn't also cheaper.

But I still think a cheap, strong, and corrosion-resistant (or -proof!) metal would be revolutionary. For all the structural uses where plastic won't do. Vehicle frames, airframes, bridges, tooling, etc. My holy grail here is something that's basically aluminum, but without the fatigue issues. Oh, and closer to steel in cost.

[eternityforest]

All-carbon cars seem pretty doable.

Tools and bridges are harder, but there's always dry nitrogen. Not sure why we don't have toolboxes with integrated solid state dehumidifiers yet, or bridge cables in rubber tubes of pressurized dry air.

[Animats]

There's a lot to be said for stainless steel. But look at the price of chromium.

[function_seven]

Right. I guess a replacement alloy would be the best bet. No matter how cheap your improved process is, the input costs are still there.

Or an improved process for extracting and refining chromium itself. Aside from cost, I think it’s a dirty process as well?

[kortex]

Yeah, chromium and nickel, two of the chief components that put the stainless in stainless-steel, are rather toxic in most/all oxidation states (Cr3+ is weirdly biologically necessary but toxic in high doses). Their refining process is pretty nasty too - lots of cyanide / carbonyl (monoxide) complexes, and mining is just generally filthy.

Automation and cheaper electricity would drive down the cost of recovering metals from aqueous waste.