I may be mis-reading, but some of the statements from the link provided seem like they could be probematic for a do-it-your-selfer inside a 40 foot pipe. I think mineral spirits has extremely strong fumes. I would not want to be inside a 40 foot pipe using ammonia, Mineral spirits, turpentine, epoxy, ect....
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In order to provide a good adhesion profile for the paint, the galvanized surface must be flat with no protrusions and slightly roughened to provide an anchor profile for the paint system"
"A solution of one to two percent ammonia applied with a nylon brush""Mineral spirits, turpentine, high-flash naphtha, and other typical cleaning solvents can be used to clean galvanized surfaces"
