cast iron hull painting

[trowell]

greetings one and all from north wales. The keel on my elizabethan 30 has not been stripped back to bare metal for what appears to be quite a long time. i spent the day scraping and grinding old antifoul and flaking sheets of rust and I now have one half of it back to bare metal. i was going to paint it with primacon but various "boat yard" wallahs say that red oxide primer is better and much cheaper, indeed I now have both types of paint on my boat ready to apply. What i'd like to ask is should I apply a rust inhibitor like KURUST before I apply the red oxide or can i apply the latter without another product first. any thoughts on this would be good reading matter to accompany my current beverage. thanks to all that can be arsed to reply

 

[Ubergeekian]

What i'd like to ask is should I apply a rust inhibitor like KURUST before I apply the red oxide or can i apply the latter without another product first. any thoughts on this would be good reading matter to accompany my current beverage. thanks to all that can be arsed to reply

I have had very good results using POR-15 Metal Ready, which is available from Frost.

http://www.frost.co.uk/item_Detail....&frostCat=Rust&frostSubCat=POR-15&subCatID=37

 

[Pasarell]

Red Oxide Primer

I would seroiously doubt the sanity of your advisers. Red oxide primer will be as much use on your keel as a chocolat teapot! There are some very good primers that are a similar colour but unless you have one of those (and have prepared the surface suitably for it) put it in the skip and go back to Primacon.
Red oxide has no anticorrosive pigment content and is probably not suitable for immersed use either.
With the preparation you describe I suggest you pressure wash the bare iron a couple of times to get as much salt out of the pores as possible then regrind to remove the flash rusting that will come from washing before first coat of Primacon.
Getting the right number of coats of Primacon on is important - don't skimp on that

 

[gasdave]

I would echo Pasarell comments - surface preparation is key. You need to get back as far as possible to bare clean metal which means either blasting, or at least some serious grinding or wire brushing. The surface should then be de-greased and any residual rust treated with a rust inhibitor/converter (I used 2 coats of Fertan but there are others).

Personally I would not use red oxide on your keels - there is nothing in their datasheet/product descriptions which suggests it is appropriate for immersed areas. Primacon on the other hand is but follow the instructions and don't skimp on coats (minimum of 5) - this needn't take long as it is very quick drying.

Having said all that there are comments on another recent thread on this site impyling that Primacon is not adequate either and that epoxy coats ought to be applied as a base (they are now using this on the Forth Rail bridge so that they can eventually stop painting it - more unemployment!).

It all depends on what sort of longevity you're after.

 

[cliffordpope]

People loosely use the term "red oxide" when they are really thinking of old fashioned red lead primer, which remains unsurpassed for priming ironwork anywhere.

The best you can say about red oxide is that it is red.