What are the pros and cons of cast iron vs. porcelain covered steel bathtubs? I'm wanting a free standing bathtub but do not want the fiberglass or acrylic type that are common now.
Great call. Cast Iron's bottom & sides are solid, none others are. Steel is quite bouncy & hollow sounding. Cast Iron is very heavy so consider that if you'll be installing yourself. You'll want 3 other helpers & to make a stretcher under its rim out of 2x4's & treat it like a King or Queen...unless winding stairs or shallow hallways will be a length issue.
Claw foot tubs cost more than modern steel tubs by about one order of magnitude, but you sure do get what you pay for.
A cast iron tub will survive being removed and installed multiple times, whereas a steel one might need to be replaced in your lifetime. They're ~$150, why would you ever reuse an old and abused steel tub?
A used and slightly abused claw foot tub is worth repairing however, if it ever becomes damaged, and should serve you well until the end of your days. Provided, you never chip the enamel and don't use any incorrect cleaning products on it. This applies to both types, but cast iron tubs are much more tolerant of abrasive abuse and impacts, as they generally have a thicker coating of enamel.
steel is flexible and i have never actually seen a freestanding steel tub (i would be interested if you have). it typically is stronger than cast iron, so its made in thinner sections. steel tends to continue rusting, whereas iron tends to passivate and slow or stop rusting once it has an oxide layer.
cast iron is readily available, but its a porous material that is intrinsically brittle. it tends to be a heavier section than steel, so its correspondingly heavier as a tub.
both corrode, and both are heavy. you have to ensure the coating (porcelain, enamel or urethane) have to be kept intact. patch or wax at first sign of a chip or crack
steel tubs are easier to get into place. cast iron tubs are brutally heavy and can actually require floor and stair reinforcement just to get them into place.