Blacking with Hammerite

[Karl]

I have a problem where on the marina my boat is moored the rear of the boats base plate only sits about an inch below the water. As such all the oil,diesel etc sits on the edge of the baseplate and takes off the blacking. Someone has said paint Hammerstein smooth on the edge and then black over it whilst it is still tacky. Will this work and protect the metal longer or will it react ? I am going to be using SML paints Ballastic black. I used international last time but after a year or so it started to wear off the waterline. Apparently SML. A lot better but just want to know about theHammerite .

Many thanks.

[dmr]

Its an interesting idea so try it out, but in general most paints are just not suitable for long term immersion in water, or even standing water. Hammerite is for garden gates, not boats ?. Epoxy is the way to go, even with half baked prep a surface tolerant epoxy will be better than anything else.

 

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

[Bee]

As DMR says, ....most paints are not suitable for long term immersion etc...  they blister, peel, bubble and generally detach themselves from the surface. Another vote for epoxy.

[MarkH2159]

Have to ask...

How come the boat sits so shallow in the water?

How come there is so much oil, diesel, etc in a marina to have such an efffect on paint?

[nbfiresprite]

1 hour ago, MarkH2159 said:

Have to ask...

How come the boat sits so shallow in the water?

How come there is so much oil, diesel, etc in a marina to have such an efffect on paint?

He means the uxter plate, And if you moored close to the refueling point, repeated spills will have an effect over time.

[Dr Bob]

"and then black over it whilst it is still tacky."

 

Let me pick up this bit.

Please define tacky. Tacky to me means the first coat hasn't finished curing i.e. It is not fully cross linked and more importantly all the solvent has not come out. If you then coat with a different coating you are likely to get attack on the bottom coat from solvent from the top coat and you are sealing in the solvent in the bottom coat meaning it never gets fully hard. Painting over a tacky first coat is a bad idea. Let it cure first.

I have been involved in paint formulation for a reasonable chunk of my working life and always paid attention to the performance of paint panels we tested. Real world performance was however king. Hammerite is fairly easy to apply especially over poor surfaces so if this worked well, everyone would be doing it. Hammerite has been around for 40 years +. They haven't - so very unlikely it will do any good. My guess is the hammerite is too rigid and brittle and lacks the adhesion of epoxy so won't last very long. Once on it is likely to be very difficult to get it all off to black properly. 

I'd move marina.

[pearley]

Talk to SML and see what they recommend. In my case it was 2 coats of Vinyguard primer before the Ballistic Black. You might scrape the blacking but the primer stays put.

[David Schweizer]

13 hours ago, MarkH2159 said:

Have to ask...

How come the boat sits so shallow in the water?

How come there is so much oil, diesel, etc in a marina to have such an efffect on paint?

I suspect he is referring to the Uxter Plate, and the section which is being affected by the oily water is the guard iron below the lower tunnel band, which most boaters paint with marine enamel. (See attached photo) As for the paint wearing off at the waterline, surely most boats do that, which is why I always used to lay a couple of extra coats of blacking onto the waterline.

 

 

 

[BWM]

You can buy an underwater primer which would give you a good base for your chosen top coat.

[blackrose]

8 hours ago, pearley said:

Talk to SML and see what they recommend. In my case it was 2 coats of Vinyguard primer before the Ballistic Black. You might scrape the blacking but the primer stays put.

 

Jotun Vinyguard or International Primocon - having used both they're pretty much the same thing, but I think Primocon might be available in smaller quantities. They're good primers for a few years underwater - last about a year or two longer than the blacking in normal circumstances. I don't know what the resistance to diesel would be like but if I wasn't going to use epoxy then it would be my first choice of single pack primer for underwater hull areas.

 

Primocon_AP_eng_A4_20190605.pdf (international-yachtpaint.com)

Edited February 23, 2021 by blackrose