When engineers become plumbers. What condition of chemical reaction is dissolving a cast iron pipe? I'm generally curious if this is accurate. Especially in over the counter products. A guess of mine is that the damage from chemical treatment of old metal pipes (including thinning copper drains) is caused more so by the expansion created when the chemical reaction heats up. And it does fast. This expansion can cause thining metal to crack.

Glass lining of cast iron tanks is a thing in the boiler industry.

i would guess that the corrosion and deteration of CI drainage systems you are referring too is more likely caused by old age. To prevent further deterioration where replacement isnt an option they can install a liquid liner that is more of an epoxy.

But like some else said. PVC or ABS.