I don't see why people say "Industrialism would have ended slavery!"
Have people forgotten the horrible conditions (and wage slavery) of the late 1800s, early 1900s? Can you -seriously- imagine slave owners going "Well, I have all these black slaves, and I have this factory I want to build/man... Better free them and hire some other guys."
It doesn't take much more skill to man a factory as a floor-worker than it does to be a cotton-picker.
Slaves have to be fed, housed, etc, and at the same time are far less motivated (and trained) than other workers. The costs of running a slave factory would be very high compared to just hiring regular workers.
They don't
really have to be fed, housed, etc. Some of the first things that could be called industrial-age factories were Caribbean sugar mills, staffed entirely by slave labor. They were a major cause in the rise of the Atlantic slave trade, since slaves at sugar farms and mills rarely lived more than five years (mills in particular were nearly guaranteed accidental death). You don't need to worry about the welfare of your workers when you expect their job to kill them sooner than deprivation.
Plantation slaves in the US were comparatively better treated, partly because by the 19th century the planters knew they had to keep their slaves alive or they'd run out. And even then, the industrial cotton gin was used by more slaves than free men until the Civil War, and was called a major cause of slavery's survival by abolitionists of the day.
I just felt like throwing that out there. Point being, slavery ended in all the places it ended because
relatively forthright people in power wanted it to, not because it became economically prohibitive. Brazil didn't abolish slavery until 1890, and even then only by edict of Brazil's monarchy. As poorly treated as factory workers would become, people who literally have no other choice than to work for you are always cheaper to keep.