my camper bed-end poles are full of something similar... but I thought they must have been delivered like that cause that hadn't been wet. I thought it was some kind of powder, like talc. I haven't tried to clean them.
If you pack up in the wet, at the next opportunity (at next stop or when you get home) take them out and extend them so they can dry completely.
Here dunno if this will solve your problem but aluminium pots filled with water and boiled with letric soda cleans metal (including the alluminium pot)
So i guess if you get a pot (doesnt have to be alluminium if your cleaning alluminium) and fill it with water and letric soda and boil then put the ends of the poles in this should enable the corrosion to be cleaned off easily - ladies this works well for silver wear and jewlery too
A place I'd rather be... Mitchel Road, Bomjinna. Central West Victoria (Jan '08)
After any trips to the beach or similar, once home i pull all the poles apart and wash them/wipe them down with water and let dry. Once dry, i spray them all down with lanolin or WD40. Seems to work well.