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Primer on Steel Hull


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I have a steel narrowboat, 13 years old. The previous owner has applied a primer to the metal before the blacking.

 

The blacking is sticking to the hull in places but not in others.

 

Obviously i can only clearly see this above the water line.

 

Should i be concerned and what should i do about it.

 

My initial thoughts are that if there is either primer of blacking between the steel and the water its probably ok for rust prevention but poor for visual appearance,

 

I would appreciate any advice from people with more experience of this topic.

 

 

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Did you know this before you bought it? What did your surveyor say about it?

 

If you didnt know before, can you tell what kind of primer it is. I'm fairly sure I used International Primocon in places on my hull when I last blacked it, and I cant see any evidence of problems, (although I may find some when lifted out in early September :) )

 

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3 minutes ago, Iceni_exporer said:

I would appreciate any advice from people with more experience of this topic.

 

 

Have a read of this thread for a 'worse case scenario'.

 

The main problem is that the microbes are anaerobic and can continue to live beneath the existing paint coatings and, once sealed in with a fresh blacking, the lack of oxygen and light is the perfect environment for them to thrive leading to a risk of corrosion out of sight.

 

 

 

 

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32 minutes ago, Iceni_exporer said:

I have a steel narrowboat, 13 years old. The previous owner has applied a primer to the metal before the blacking.

 

The blacking is sticking to the hull in places but not in others.

 

Obviously i can only clearly see this above the water line.

 

Should i be concerned and what should i do about it.

 

My initial thoughts are that if there is either primer of blacking between the steel and the water its probably ok for rust prevention but poor for visual appearance,

 

I would appreciate any advice from people with more experience of this topic.

 

 

If the blacking system applied last time round has partially failed then book it in for re-treatment sooner rather than later. You’re never that long between treatments so there’s no great extra cost overall. Then you can have a good look at the hull as well. It isn’t going to sink at any time in the near future as a result of this problem and it’s no more or less susceptible to the orange steel munching bug that Alan is obsessed with. I have no idea why he thought that a relevant or even wise response. I doubt there’s a steel narrowboat out there without some exposed metal in any case.

 

JP

Edited by Captain Pegg
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Primers are not normally used on steel narrowboats, the blacking itself is designed to stick direct to the steel, even slightly rusted steel. Some primers Might help but many will be counter-productive, especially below the water line. As you don't know what the primer is its a bit difficult. When you get the boat out of the water then if the primer is well stuck on after the pressure wash then maybe leave it on and black over the top. If the boat shows any significant pitting then a shot blast and epoxy will really help but that does cost a bit.

 

...............Dave

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Before I switched to epoxy I used to put a couple of coats of International Primocon primer on my boat prior to blacking. It sticks to the steel better than blacking and extends the times between blacking by about a year. It's made for above or below water applications. A very similar product called Vineyguard is made by Jotun. They're both silvery single pack paints. 

 

If you're fortunate the previous owner will have used an underwater primer but some idiots think ordinary red oxide or grey zinc phosphate primers can be used below the waterline. 

 

It doesn't really matter that much. Whatever is on your hull, if it's covered with bitumen you'll have to get the boat out the water within a couple of years, pressure wash it and put more bitumen on top. It's garbage and doesn't last long however well you apply it.

 

 

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