Spoke to the paint rep yesterday. He recommended not to soda blast as it leaves a residue which is very hard to get rid of. Has to be water blasted at a very high pressure and even then very hard to get it all off. The secret to paint adhesion is clean. He also told me that yes Volvo do recommend an etch primer first but the problem is they don't know whether the boat is going to be full time in the water or on a trailer most of the time so they just use an etch primer on all their legs. Apparently Zinc chromate primers are not designed to be immersed full time. No problem if it spends most of its time on a trailer. I have been recommended to grit blast it with garnet and prime it with an Altex #1 primer which is designed to go straight on to the Aluminium. I have used this product before, it sticks to practically anything and is very hard wearing as it is a 2 pot primer. It is also designed to be immersed full time.
Also spoke to 2 different grit blasting companies and they both recommended garnet as the blast medium for the same reasons. 3 out of 3 from the experts so that's the way I've gone. We also happen to have a grit blaster at work with garnet so that also saves paying to have it done. Did the blasting after work yesterday and it made a really good job. Then degreased it with a degreaser that leaves no residue. Put the primer on last night. Been told to get the primer on within a couple of hours of doing the blasting as the Aluminium starts oxidizing very quickly. Looks really good so far compared to the 5 coats of anti foul that were on there. The boat should go a lot faster now without all those extra coats weighing it down.
