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I'm very confused, the article says:

'The MTA had good reason to believe the program would succeed. Just a few years prior, it had dropped more than 1,000 Redbird trains in the ocean. They remain on the ocean floor to this day, in part because they were made of carbon steel, which helps prevent corrosion.

By comparison, Brightliners were made of stainless steel. When the subway cars debuted in 1964, they were a mechanical and aesthetic innovation. The stainless steel made the train cars lighter on the tracks, but this worked against them underwater.'

Few questions here. First, isn't carbon steel ... steel? Steel is primarily iron and carbon, so my understanding is that carbon steel is mostly just a marketing term to have at least an adjective of some sort, just like 'aircraft grade aluminium', which is in fact one of the cheapest, bulk types of aluminium (hence use in bulk in aircraft)

Second, how does regular steel fare better than stainless steel in a corrosive environment? The article says the stainless steel started to corrode from the welds, which is fair enough, but wouldn't regular steel just corrode wholesale?

discuss

skateboardCat|4 years ago

Carbon Steel is the name of "regular", non-alloy steel.

And w.r.t. the SS thing, i think the carbon steel got to be thicker because of expected corrosion while the SS (that still can oxidize, albeit at a much slower rate) is significantly thinner, therefore getting disintegrated more easily.

It really isn't worded very well in TFA tho, i may be misunderstanding.

cardiffspaceman|4 years ago

I think the basis could be that the newer trains were too light to stay sunk, being made of a material that is lighter yet stronger. Also it so happens that construction details matter. The article cites corrugation, which allows panels to be lighter yet just as strong. The article also cites spot welding. You can weld together steel panels in many ways, and the article doesn't say how the Redbird cars were constructed, except there's an implication that there's no spot welding. The Titanic was made of "iron" as the dramatized architect said in the movie, but he seems to speak poetically [1][2]. The ship hasn't quite dissolved like an aspirin.

[1] https://www.moviequotedb.com/movies/titanic/quote_23821.html [2] "The 2,000 hull plates were single pieces of rolled steel plate" https://en.wikipedia.org/wiki/Titanic#Building_and_preparing...