I'm wondering the same. And what the cleaning chemicals were (I suspect the first was an acid, to remove rust). Lastly, what was that red/gold rust inhibitor?
Much of the work is necessary, but not the way they did it. Workers were exposed to possibly dangerous chemicals and known dangerous dust. Those guys should have full respirators and with work in a negative pressure extractor hood, to remove most of the airborne dust. The rest is just manual labor, which could have been automated (if labor prices weren't so low). The human toll on this manufacturing is staggering.
