MardyBum

Thank you!! I will give them a call on Monday 👍🏻 I had looked at Rawlins before, but evidently not thoroughly enough! Regarding the new outlet fitting, I'm gonna get the old one welded up and then fit a new one at the top of the tank with a dip pipe. I figured that will make for easier serviceability and reduce the risk of a full tank of water leaking into the bilge should there be any kind of fitting failure (thanks @Ex Brummie). Will post some follow up pics in due course.

Yep - SML were my first call, but they said I would not be able to get the surface prep good enough without grit blasting - apparently it's not surface tolerant (ike Jotun 90 is for example).

I think this or what @Tracy D'arth suggested is what I'm leaning towards at the moment, although interesting idea about fitting at the top of the tank with a dip hose, from a failure protection perspective I quite like that too - thanks all! @ditchcrawler if I could find a surface tolerant potable epoxy that's exactly what I'd be doing, but I've so far come up short. All the previously recommended products have been removed from sale in recent years. If you know of one still available, please do share 🙂

We're currently de-rusting our integrated water tank and are planning to paint with 2-pack epoxy (as we have done for the bilge bays) and then use a separate smaller tank for drinking water. The boat is out of the water in a couple of weeks and we've a welder booked in to fill a number of deep-ish pits. The outlet pipe (top left in pic below) inside the water tank is all bunged up with rust and pretty gross. I was thinking of cutting it off and asking the welder to weld on a new one, perhaps pre-painted with epoxy as much as possible (up to the point of the weld area, obviously). Is there a better way of doing this? I'm not really sure what best practice is here, and I've effectively got the opportunity to start again with it! Can I/Should I use some sort of plastic piped or ask him to weld on maybe a threaded hose tail connection through the tank wall with a hose down to the tank floor? Thanks folks.

Yeah I know you're probably right. Sometimes it's helpful to be told what you already know though 😆

Evening all - still slogging away at the bays down the boat. Came across a deepish pit on the hull side (6mm steel), below the water line (around 2.5mm max deep I reckon, inch or so wide) and wanted a steer/sanity check on options. As this is inside the boat, I was considering cleaning the pit out to shiny steel (done) and then just filling with an appropriate 2-pack filler and painting over with the epoxy. Other option is to get it welded, but for an internal pit of this depth, is it necessary - f I can stop the corrosion and fully seal it? Thanks folks.

This is all very interesting, I was not aware you could 'over-anode' - learning every day! I will do a bit more research. For info, we're 48ft and currently have - on each side - two at the bow, one more worn than the other (I think they just left the oldest one on), one midship and two at the stern (again, one significantly more worn than the other). My plan was to remove the anodes midship and the really old at bow/stern, and replace with two either side of the midship so the spacing between anodes was a bit more even, roughly 12ft apart. I welcome discussion/suggestions/scepticism/outrage... 😂 Based only on my observations of our base plate after it had been pressure washed, I would question this. The base plate had some pitting and corrosion all along the length, with the exception of the areas immediately adjacent to and a few of feet either side of the existing anodes - the steel seemed almost unbelievably smooth and flawless. I came to the conclusion that this was evidence of the anodes doing their job and protecting our base plate too 🙂

Did that early summer last year after we bought the boat as it was long overdue - went for the SML surface tolerant 2 pack epoxy, 3 coats. It was more of a stop gap though as there's quite a bit of welding that needs doing and there were some signs of MIC (only realised this after the fact, however). It'll be coming out this summer for grit blasting, welding, additional anodes and then proper 2 pack. Might go for the zinc coating, haven't decided yet. @dmr Thanks! Hoping to do all this properly now, once, so I don't have to worry about it!

Update 2: Onto 4th and 5th bays now with the Jotamastic 90 (winter grade). Seems to be taking and curing well, I know the temperature and humidty outside at the moment is not ideal, but I've got around this with a couple of oil rads a dehumidifier. So far so good, although I guess time will tell. Taking a lot of time with prep as I really don't want to have to do this again anytime soon! Angle grinder and combination of wire wheel and stripping discs seems to work well. Have had to use a hammer in places to loosen thick scale, then going over any polished metal with the sander to key up the surface. Lastly a good vacuum (or several) and a degrease/wipe down with pure isopropyl alcohol before painting.

Thanks all - will get in touch with Wincham. @Tracy D'arth just to clarify, did you have your boat grit blasted/epoxied there?

Resurrecting this to ask (on the off chance they still check the forum) @WillCful where they ended up going in the end, or if anyone else has had a good grit-blasting/epoxy experience at Aqueduct, Swanley, or anywhere else, midlands/northwest way recently? Have had quotes from Debdale (who we've we've used previously for other work, but are far from home) and Aqueduct (who are closer, have a good sales spiel but have had a number of less than favourable reviews recently). Ta!

Update: Using an angle grinder with a wire brush cup and going with the Jot 90. They do a winter grade version so not too worried about application temps, for the moment at least. I can't do anything about the bays I've already done (partially built over them) but going forward it's epoxy all the way 👍🏻

Thanks for the advice. @David Mack I am sure you're right regarding the prep in these areas. I was very conscious of giving the vactan enough time to try, and the areas of good steel with minimal corrosion/pits seems fine - vactan and paint both adhered well. @blackrose Funnily enough I was looking at Jotamastic 90 the other day, but assumed that the surface would need prep beyond what is practical for us (i.e. grit blasting). @john.k What is flame spalling, as a technique? Google was not helpful!

Evening all. We're currently in the process of gutting and redoing out boat. After clearing out the gunk and rust scale from our bilge bays we applied two coats of vactan, let it dry for several days, then two coats of bilge paint. All seemed well. Now, three months later, the paint is bubbling and it looks like some micro-pitting and corrosion, or at least rust to some level is evident beneath the paint, fairly pervasively throughout the bays, as per the example in the pictures (in order - painted; scraped back; wiped clean). Is there anything I can realistically do, short of shot blasting or grinding everything back to bare steel, to completely eliminate this? Thanks folks.