Propeller Antifouling

[Kashmir]

I am the proud owner of two new Brunton Auto-props which I will fit in a couple of weeks. Having recovered from the CC hit I decided to anti-foul the blades (which are a SS variant) with Velox Plus. Rather than use the Velox primer I've opted for Hammerite Special Metals Primer instead on the advice of this forum. On attempting the first coat today I had to abort and wash off the primer. I could tell straight away that it wasn't going to stick as each brush stroke left streaks where the paint hadn't adhered correctly to the metal. I know that preparation is key here and I spent considerable time abrading the surface with an orbital sander and 80 grit paper (see attached photo). I then degreased with 100% acetone. After removing the first coat attempt, instead of using the acetone, I washed the blades in soapy water and dried as recommended by Hammerite themselves. Unfortunately the same happened with the paint wanting to sit on top of the surface.

Am I missing something here? Perhaps the new water based Hammerite SMP is not suitable for stainless steel...

Do you think I will have better results with Marlin's own primer instead?

Thanks for any advice.

 

[RivalRedwing]

Hi
It sounds like you are doing all the right things although I would use a finer (probably wet and dry) grin to key in the surface (say 300 grit + water) and do it by hand to ensure full coverage. Finish off with some warm water and a hand washing detergent such as Daz and a sponge, and then a final rise with water to remove detergent residue, then leave to dry overnight. Use several thin coats of the special metals primer and don't worry too much about achieving 100% coverage with the first one.

 

[Pye_End]

Don't overbrush. Better to go 2 coats to get rid of bigger blemishes.

There's a Velox Youtube video somewhere which is quite helpful. edit. might be Facebook.

 

[vyv_cox]

Are the Bruntons blades stainless steel? (They do look it in your pics) Hammerite is great on non-ferrous, zinc, aluminium, copper alloys but not sure how good on stainless steel. It is most unlikely to etch it, the reactant is KOH, which probably has little effect on SS.

 

[Kashmir]

I would use a finer (probably wet and dry) grin to key in the surface (say 300 grit + water)

Thanks, I was trying to follow the advice given in this video. They say the rougher the surface the better for adhesion...

 

[Sandy]

I fitted a Brunton years ago. Never put anything on it.

 

[Kashmir]

Are the Bruntons blades stainless steel?

Yes I believe they are a variant of SS. According to Hammerite, their special metals primer is suitable for SS but I do know there are many variants and I'm sceptical in this case as the paint seems to want to sit on the surface and brushing it just seems to move it around. I might try Marlin's own primer which is likely not water based and see if that works. There is a video from PYI showing the application of Velox Plus on a prop blade and it seems to go on fine: How To Apply Velox Plus

 

[Kashmir]

I fitted a Brunton years ago. Never put anything on it.

Thanks, I presume you srub it at the end of the season? What is the growth like? I'm UK south coast based.

 

[vyv_cox]

Thanks, I presume you srub it at the end of the season? What is the growth like? I'm UK south coast based.

My Bruntons has copper alloy blades. It used to foul badly in Greece, mainly tube worm. With Hammerite and Velox it is almost totally fouling free nowadays.

 

[RivalRedwing]

Thanks, I was trying to follow the advice given in this video. They say the rougher the surface the better for adhesion...

how big do you expect the molecules of paint to be?

I've used special metals primer + Velox to grest success on Darglow Featherstream blades which are 'stainless steel 316 heat treated blades' according to Darglow.

 

[Kashmir]

My Bruntons has copper alloy blades. It used to foul badly in Greece, mainly tube worm. With Hammerite and Velox it is almost totally fouling free nowadays.

Yes, I followed your previous threads and it is the main reason I chose this method. However, given my blades are SS, maybe I need to rethink....

 

[Kashmir]

how big do you expect the molecules of paint to be?

Approx 1 micron.

 

[Kashmir]

I've used special metals primer + Velox to grest success on Darglow Featherstream blades which are 'stainless steel 316 heat treated blades' according to Darglow.

Interesting. And you didn't get any of the adhesion problems I've mentioned with the primer? I know they have changed the formulation to water based recently so maybe that's the problem.

 

[RivalRedwing]

nope, I used the water based version

 

[Pye_End]

nope, I used the water based version

Ditto.

 

[Sandy]

Thanks, I presume you srub it at the end of the season? What is the growth like? I'm UK south coast based.

The boat came out of the water at the end of COVID 18 months doing only 12 NM and all I did was hose it down with fresh water.

Plymouth based.

 

[vyv_cox]

Interesting. And you didn't get any of the adhesion problems I've mentioned with the primer? I know they have changed the formulation to water based recently so maybe that's the problem.

Always been water based in my experience. Not sure how a solvent based etch primer could work.