Tuesday 18 of October, and we're on the hardstand in Aktio Marina in Preveza.
This morning, after a stormy but very restful night, there was a very loud racket being produced by something a couple of boats away. It turned out to be a sand-blasting operation. Great, just what we needed. We talked with the boss-man Panos and our fears of an Australia-size hole in the budget turned out to be unfounded. About €550 to blast the keel, fill the holes with 2-pack epoxy filler and seal it with epoxy metal primer. And it can be done within a couple of days, even better as the next stage consists of putting 4 layers of 2-component epoxy primer on, each with about ½ day of curing/drying. Something we can do much cheaper ourselves.

WARNING: TECH STUFF!
The keel and its problems. Last year we spent a fair bit of time, money and elbow grease on trying to stop the rusting of the keel. After about four weeks in the water, the keel was rusting even worse than before (top-left photo), so obviously there was something we didn't do right or we didn't properly understand.

The keel always looked a bit pitted here and there, it looked like the keel metal was electrolysing in places. Not that I could understand why, because there were no bi-metal connections exposed to seawater.
Anyway, Stephan the gifted German engineer, suggested that the rust problem was best attacked with some 'bite the bullet' sandblasting approach. I thought that was a bit over the top and a steel brush on a drill, applied at the rusty spots, should do the job. Well, we tried that last year and it failed. Maybe Stephan was right and we decided to bite that bullet as well and we hired Panos (top middle photo) to do the job. He turned out to be an excellent choice. Not only did he blast sand at keels, but he's also able to gently blast antifouling from the underwater hull without damaging the gel coat, repair structural polyester and gelcoats, and paint whatever needs painting.

So Panos and I got talking about the keel and the rusting and I ventured my opinion about the cause of the pittedness being electrolysis. He corrected that idea by explaining that the unevenness is not some erosion process, but the result of the keel being casted steel. Ahhhh, a penny dropped, now that explained everything. In the process of pouring the liquid iron into the keel mould, air bubbles get trapped along the wall of the mould, causing the pitted surface (bottom left photo). After the metal cools down, the factory fills the 'valleys' with some polyester compound and that's how they get a more or less smooth surface. But if you look a bit closer at the keel's surface after sandblasting (see details on bottom left photo), you can see that some of the 'dents' extend under the surface well beyond the opening and as such form small subsurface 'caves'. Things like steel brushes (likely to introduce more rust) or sandpaper will never reach inside those little caves. As we know, rust (iron oxide) on a steel surface (especially in the presence of sea water) will facilitate the electrochemical rusting process in a positive feedback way: rust accelerates rusting. Once rusting starts inside those little caves under the surface, there really is no other/better way to remove the rust than by sandblasting, and so resetting the rusting process. By quickly putting a metal primer on (making sure it gets into those little caves) before water and oxygen in the air can start the oxidizing (rusting) process again, we effectively set the keel back to the time it came out of the mould. Excellent, we now much better understand the process. Thanks Panos!

Now to the practice of it all. Panos and his team rock up with a fairly sizeable compressor to blast the keel with a very abrasive (glass I believe) grid. As the grid pulverizes upon impact, both the blaster and the environment need some protection. The blaster has a positive pressure helmet and a small tent is erected around the blasting area to contain the dust and stray grid (top-right photo). The whole process is done fairly quickly, it took just over an hour to blast our keel. Straight after the blasting, they applied a two-component epoxy steel primer (bottom, second from the left), making sure it covered the inside of the subsurface caves. Once the primer is on, the most time-critical work has been done as moisture and oxygen is now excluded from the metal. The primer is to cure and harden for about a day. Next day the bigger dents and caves are filled with an epoxy filler (bottom, second from the right) which needs to cure for another 24 hours and sanded down where necessary. If you sand through the original primer, you need to reapply it. In our case Panos was very prudent in just putting another coat of metal primer over the whole keel.

Well, that was their work done: very expertly, timely and with some great info on the side. Unlike many others we worked with, Panos arrives when agreed, actually responds to emails and keeps us up-to-date, something we really appreciate being so far away. We liked very much working with him, let us know if you need his details. Thanks a lot Panos and his team!

Over the next couple of days, I applied four coats of epoxy (not steel) primer, with its main objective being to protect the keel. The lady manning the Aktio chandlery suggested to use different colors between layer so you can better see what you're doing. It turned out to be an excellent suggestion. Before she (Clio, not the lady) goes into the water, we have to put on an underwater primer to allow the antifouling paint to stick better to the keel. But that is for April next year. So far, working in and with Aktio marina has been a very positive experience, even with the mozzie legions.