This isn't painted or oxidized. It actually looks just like corrugated metal. Except instead of being metal it the fiber cement material.
Chris, you've done industrial pressure washing haven't you? Have you came across any of this?
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At the refinery there was asbestos insulation, shingles, siding, panels and roofing material that looks like the tin they use on barns with the ripples, kind of like what the sloped sides of a Whataburger building are made of, only asbestos.
We could not use anything that would disturb the surface, honestly they left all that stuff alone unless it was being remediated which involved plastic sheeting around the area, suits, respirators, portable showers, the whole nine yards to deal with the stuff.
If soft-spray chemical cleaning (no pressure at all, like using large fan nozzles for downstreaming like 2525 or 4015 spray nozzles) then I would not touch it. Disturbed asbestos.....you will not see or feel the affects for about 15 or so years, then it is too late, nothing they can do for you. Is the job really worth the risk?
Since the fibers that do the damage to your lungs are tiny, microscopic, you would not know if you disturbed them if you were careful when pressure washing and being that small, they float nicely in the air and unless you are using respirators with the throwaway coveralls/boots and have a portable shower there to rinse off before changing, I would not take the risk.
I had to write the permits for those kinds of jobs but never did them myself, it was the onsite contractors that did those kind of jobs as they were certified, had numerous hours of training and so many hours experience to do the job and it cost way too much for the supplies and equipment for most jobs but when it had to be done, the checkbook was open and people got paid a lot.