geoff
New member
My Leisure 23SL has twin cast iron bilge keels.They are covered in large nodules of rust.After chipping off the rust what should I use to slow down re rusting before I anti foul?all contributions gratefully received!!!
Rusty Keels
- Thread starter geoff
- Start date
KenMcCulloch
New member
Zinc paint such as Galvafroid can be succesfully used on iron keels.
Thamesbank
New member
Phosphoric acid
Kills the rust dead. See: Acid info
Then clean and cover with zinc paint or epoxy or whatever.
Kills the rust dead. See: Acid info
Then clean and cover with zinc paint or epoxy or whatever.
JasB
New member
Re: Phosphoric acid
do hammerite do a primer?
do hammerite do a primer?
DickB
Member
Re: Phosphoric acid
Graham at Aladdins cave in Mercury reckons on this stuff G4 (bonda marione) is good for that... Maybe worth a look...
cheers
Graham at Aladdins cave in Mercury reckons on this stuff G4 (bonda marione) is good for that... Maybe worth a look...
cheers
oldsaltoz
New member
[ QUOTE ]
My Leisure 23SL has twin cast iron bilge keels. They are covered in large nodules of rust. After chipping off the rust what should I use to slow down re rusting before I anti foul?all contributions gratefully received!!!
[/ QUOTE ]
G'day Geoff,
You may have noticed that when you do a spot repair on a cast iron keel you will get another rust spot develop close to it next season, this is due to the fact that cast iron is porous from new, the casting will have voids containing impurities that allow water to enter them, as this is not too far from the surface the water will have some oxygen with it and rust will form. Cast Iron will oxidise in seconds if blasted or ground in an effort to protect itself from oxygen.
What this all means is that if you want to stop rusting you need to take action that will prevent water contacting the surface of the cast and, make provision for any very minor pin holes that may occur later.
The tried and true method is to remove any existing rust, blasting or acid and get a coat of zinc on it before it starts to rust. If blasting this means having a long handle brush and zinc based paint applied as soon as the blasting nozzle is moved a couple of inches. Also note the thickness of this zinc coat is critical as too thin it will not work, too thick it will mud crack leaving the coating too thin at the crack lines; best dried thickness is around 95 microns, but check this with the manufacturer before you start, a simple painters comb will show when you have the correct 'wet' depth that will give the correct dry depth when the paint goes off, zinc paints dry in minutes not hours, but need 24 hours to fully cure.
Having got the zinc on at the right thickness you now need to protect it and the keel from getting wet. 3 or 4 coats of a good epoxy wet on tacky seems to be one of the best, and applying wet on tacky avoids the need to wash then sand, then wash and dry before re coating.
Now you need to protect the epoxy. Keep in mind you will want to scrape off any shell growth at some time in the future so the coating needs to be thick and hard, I have used the paint they apply to marina steel piles with good results, it goes on easy and dries to around 1mm+ thick.
Let this cure for a few days, give it a light sanding with a 150 grit and apply two coats of antifoul.
Avagoodweekend......
My Leisure 23SL has twin cast iron bilge keels. They are covered in large nodules of rust. After chipping off the rust what should I use to slow down re rusting before I anti foul?all contributions gratefully received!!!
[/ QUOTE ]
G'day Geoff,
You may have noticed that when you do a spot repair on a cast iron keel you will get another rust spot develop close to it next season, this is due to the fact that cast iron is porous from new, the casting will have voids containing impurities that allow water to enter them, as this is not too far from the surface the water will have some oxygen with it and rust will form. Cast Iron will oxidise in seconds if blasted or ground in an effort to protect itself from oxygen.
What this all means is that if you want to stop rusting you need to take action that will prevent water contacting the surface of the cast and, make provision for any very minor pin holes that may occur later.
The tried and true method is to remove any existing rust, blasting or acid and get a coat of zinc on it before it starts to rust. If blasting this means having a long handle brush and zinc based paint applied as soon as the blasting nozzle is moved a couple of inches. Also note the thickness of this zinc coat is critical as too thin it will not work, too thick it will mud crack leaving the coating too thin at the crack lines; best dried thickness is around 95 microns, but check this with the manufacturer before you start, a simple painters comb will show when you have the correct 'wet' depth that will give the correct dry depth when the paint goes off, zinc paints dry in minutes not hours, but need 24 hours to fully cure.
Having got the zinc on at the right thickness you now need to protect it and the keel from getting wet. 3 or 4 coats of a good epoxy wet on tacky seems to be one of the best, and applying wet on tacky avoids the need to wash then sand, then wash and dry before re coating.
Now you need to protect the epoxy. Keep in mind you will want to scrape off any shell growth at some time in the future so the coating needs to be thick and hard, I have used the paint they apply to marina steel piles with good results, it goes on easy and dries to around 1mm+ thick.
Let this cure for a few days, give it a light sanding with a 150 grit and apply two coats of antifoul.
Avagoodweekend......
jleaworthy
New member
Having tried just about all the suggested remedies - without success, and unable to keep a decent coat of antifouling on the cast iron keels because of the underlying corrosion I decided to try fixing an anode to each keel. I chose large button anodes (cost about £17 each) and fixed each one with a single 10mm stainless steel bolt threaded into a 10mm tapped hole in the middle of the outside face of each keel.
It worked. The anodes last about a season and a bit. The antifouling stays in place and the corrosion is practically non-existent. Not cheap but effective.
It worked. The anodes last about a season and a bit. The antifouling stays in place and the corrosion is practically non-existent. Not cheap but effective.
geoff
New member
thanks to everyone...at least I know why it happens!!!Its about now I wish my son wanted to borrow the boat....yeah cors u can..just do this little job first!!!