Grit blasting and epoxy coating keel - good idea?

[watermint]

i wood scrap the old antifoul off by hand , then ues 60-grit - 3m orbital sanding pads what u ues with a Orbital Sander
3m pads will rip old antifoul off like buter

http://www.gradyshardware.com/3M-96...fic_src=GB&utm_medium=CSE&utm_source=GB&id=uk

epoxy a keel , Coppercoat dos a good epoxy primer what u norley do the hull with and keel,s i have ues it and its verry good stuff to ues on a good shiney cleen keel of a boat and Orbital Sander with 60-grit - 3m orbital sanding pads will do the job if ther big holes or bump,s in keel fill it with normel epoxy and then sand it back

 

[Elessar]

Well as long as you have taken steps, that's all anyone can ask.

Personally I think epoxy is too hard, forming a 'shell' which is just asking for trapped water as soon as the layer is chipped.

Maybe a particularly good primer is the answer, certainly it's preparation.

My boat has a steel lift keel and cast iron ballast bulb; as the lift part is moving in a tight slot which may well have stones around in the mud, I avoid epoxy and use 'conventional' paint.

After trying every steel treatment going, I have found Dulux Metalshield ( 1 part, but requiring its' own 1 part primer ) gives by far the best results I have ever had.

The boat is ashore on high trestles every winter, allowing keel inspection & maintenance.

Possibly epoxy may better suit a boat with a fixed keel which does not come into contact with the seabed etc, but it's naive to think a keel can survive long without some sort of impact, be it from flotsam, shore handling, whatever.

Interesting.
Can't put CopperCoat over one part, but for conventional antifoul sounds intriguing.

 

[Elessar]

I'd be more than keen to follow up, but the boat is near Bath, not Shotley, so the travelling on-cost would be prohibitive. And it's where it is to save me money....!

even with travel it wouldn't be that much, and if you have a friend who wants it done travel is halved........

 

[Seajet]

Elessar,

if you mean the Dulux Metalshield, I've been amazed by it ! Have tried Blakes Steel Treatment, Primocon, 709 Epoxy, Galvafroid, you name it, but this Metalshield stuff is the only one ever to be in good condition after a season.

My steel keel is galvanised, but after my first keel corroded badly after about 25 years despite lavish maintenance, I did some asking around.

It seems Chichester to Portsmouth is a known area for 'accelerated steel corrosion ', I got in touch with Portsmouth Uni' Marine Metallurgy Dept who came to have a look at my old keel.

It looks a lot like electrolysis, but there is nothing electrical in any way touching my boats' keel structure anywhere inside or out.

My personal theory, and I am not alone, suspects the nearby mains power cables and a marina with its' shore power etc...our club moorings guys are well aware of it, stuff doesn't last as long as it should.

BTW I have edited my earlier reference to a company, I wasn't asked but I didn't want to cause any damage since things have been sorted.

 

[Plevier]

if you mean the Dulux Metalshield, I've been amazed by it ! Have tried Blakes Steel Treatment, Primocon, 709 Epoxy, Galvafroid, you name it, but this Metalshield stuff is the only one ever to be in good condition after a season.

My steel keel is galvanised, but after my first keel corroded badly after about 25 years despite lavish maintenance, I did some asking around.

Seajet, do you mean you antifoul over the Metalshield or just leave it at that? Is this part out of the water when your keel is raised? My swing keel is galvanised steel plate. It's still submerged when raised. I know someone with identical boat who says his galvanising failed quickly and he's had to fit anodes on the plate.

 

[Seajet]

Troubador,

I don't antifoul over the Metalshield, but I know some owners who do and it seems fine; applying Metalshield over antifouling without the Metalshield primer doesn't work too well though, I'm told the paint 'pickles'.

My steel keel raises vertically into a fairly narrow slot, if paint is allowed to build up too thick it jams the keel, so I don't bother with antifoul.

The galvanising seems to be staying put, but I know from the previous 25 years with the first keel that galvanising scrapes off in time, the going up & down in the casing presumably giving it a hard time.

We are very lucky in having new keels available off the shelf, the ex-M.D.of Andersons and I set this up with the original makers, as it seems common sense that people will need them as time goes on; however only a few boats have required them so far including mine, which was galling as I go to a lot of trouble maintaining my keel, while others get away with almost nothing !

This would seem to reinforce the theory of a local corrosion problem.

Galvanising should of course be hot dip, not just sprayed.

The boat is on a half tide mooring, I'd think the lower 1' or so stays wet but I've never had fouling on the keel even when the boat has been left a long time.

I have found it worth fitting an anode, the science is sketchy as there are no electrics in my boat anywhere near the keel, nevertheless the anode does erode a little over the season so is doing something.

You may have seen my mention in an earlier post that there is some sort of 'accelerated steel corrosion' in the whole area, Portsmouth Uni' Marine Metallurgy Dept thought it might be microbes which excrete something that erodes steel ( this is happening to the wreck of the Titanic ) but my keel showed no sign of this when they came to look.

As I say, I can only guess there's a stray current from somewhere, and my mooring is close to a lot of mains power cables plus a marina...

 

[mjcoon]

Portsmouth Uni' Marine Metallurgy Dept thought it might be microbes which excrete something that erodes steel ( this is happening to the wreck of the Titanic ) but my keel showed no sign of this when they came to look.

This may be what is called "rusticles" on marine archaeology TV programmes..

Mike.

 

[Seajet]

mjcoon,

the term doesn't ring any bells, but you may well be right.

The thing is, Titanic is 12,000' down, and if I find myself in that situation or at the bottom of a 12,000' wave, corrosion will probably not be a primary concern.

 

[Plevier]

Troubador,

Thanks Seajet.
The boat I'm referring to lost its galvanising in about 5 years in Littlehampton.
Mine's had 7 years in the Orwell until I brought her to Brighton a year ago. Lifting out next week will see what's happened...

 

[Seajet]

Troubador,

one thing I always say to people selling Andersons - or any boat, particularly lift keelers - is to take lots of photo's of the keel etc when she is lifted, some with a newspaper in shot so the date may be proven.

That way should you decide to sell her, there's something to show prospective buyers; this tip particularly applies if one has to have the boat lifted for inspection by a buyer; if the deal falls through for any reason, the photo proof might avoid the hassle & expense of another lift soon.

However I hope you find everything fine and carry on with her !

 

[KellysEye]

>it lasted ten years but then rust got beneath it. I had it re-done in Greece but some rusty spots after three years need further attention.

I think the problem of failure is that whoever did it didn't use zinc rich epoxy as the first coat, which I recommended earlier.

 

[Plevier]

Seajet

https://picasaweb.google.com/106544940609481176193/Troubadour#5564921063959087186 (and various others). No newspaper I must admit (but camera datestamp)