Amazing how experiences differ with each user. The painted rims on one of my touring bikes have never made any noise, however the non-painted rims on the other touring bike squeal nice and loud. Both have stock pads that came with the calipers when manufactured. The difference is the calipers themselves. The painted rims are mated to Suntour Roller Cam brakes. Nice heavy arms, brass bushings that fit perfectly to the studs. The other non-painted rims are mated to Suntour XC Pro cantilevers, which were notorious for squeal because of the way they mount. Brass bushing as well, but the adjustment/mounting hardware makes them prone to squeal.

My suggestion is replace the calipers with higher quality calipers. Avoid the old Shimano XT articulated V-brakes as they like to squeal.