Gotcha. I recently saw these sandblasting attachments for pressure washers and wondered if they actually work. I have a 4kPSI 4GPM washer and was considering giving one of these units a try. Maybe finish it off with a 50/50 muratic acid from a garden sprayer then a rinse. I've got an old 4x6 trailer in the bushes that's in poor shape. Needs a set of new(er) hubs, wheels and tires too.