Zinc rich primer

[Roberto]

Hello,
I have read people sometimes use a "zinc rich primer" under the propeller and bracket antifouling, this year I would like to give it a go.
What type of product is it, exactly? There are the sort of cold galvanising paints, usually a resin matrix with (supposedly) 99% zinc metal powder, and other products more properly called "primer" which mostly have a zinc phosphate active component.
Which of the two should be used?
Tia

 

[vyv_cox]

The problem is getting any paint to stick to copper alloys, brass, DZR or bronze. An etch primer is the answer, water based containing KOH. Hammerite Special Metals is a proven one, no doubt there are others.

 

[Roberto]

The problem is getting any paint to stick to copper alloys, brass, DZR or bronze. An etch primer is the answer, water based containing KOH. Hammerite Special Metals is a proven one, no doubt there are others.

Thank you Vyv

 

[Bilgediver]

I do not know if it is still the case however a few years ago I showed the International Paint Rep visiting our ship some model railway coaches I had tried to refurbish but the paint kept bubbling. He advised the use of an etch primer . I asked for a recommendation in the UK and he advised that the cans of GREY primer sold in aerosols in Halfords is fine. That advice was followed and 40 years later they are still fine. One aerosol would do a prop.

 

[Roberto]

I do not know if it is still the case however a few years ago I showed the International Paint Rep visiting our ship some model railway coaches I had tried to refurbish but the paint kept bubbling. He advised the use of an etch primer . I asked for a recommendation in the UK and he advised that the cans of GREY primer sold in aerosols in Halfords is fine. That advice was followed and 40 years later they are still fine. One aerosol would do a prop.

Thank you.
Actually, I use the Seajet Shogun antifouling painted directly on the propeller, p-bracket and propeller shaft, after mechanical brush cleaning +final solvent. It sticks without problems; I haul out and renew every year.
Funnily enough, in terms of fouling the result is almost perfect on copper alloys pieces (propeller and bracket), which remain clean, whereas the stainless steel shaft if often covered by barnacles. Unpainted fittings like the rope cutter are very fouled.
The propeller and bracket are beginning to show some reddish hue. Anodes seem to do their work, they deplete and measurements with the reference electrode seem ok. I am tempted to try some paint with some basic cathodic potential to see if there is anything different. Just experimenting

 

[fisherman]

Talking of which, where can you get Galvafroid these days? Its on line, but being so heavy the postage is a lot.

 

[michael_w]

Hammerite special metals primer works a treat on props. I overcoat with Trilux for a few weeks protection.

 

[penberth3]

Talking of which, where can you get Galvafroid these days? Its on line, but being so heavy the postage is a lot.

I used to see it in the Farm suppliers, but that was some time ago.

 

[seumask]

Talking of which, where can you get Galvafroid these days? Its on line, but being so heavy the postage is a lot.

I find you can get small pots of it ebay
Fosroc Galvafroid Anti Corrosion Paint (400ml/800ml/1.9L) | eBay

I use it in very small amounts on things like keel bolts, car paint chips etc. a 400ml pot lasts many years if stored well.