Should I prime bare rudders before painting?

[sgharford]

Wondering if I should apply some kind of primer to mostly bare bronze rudders before applying ablative antifouling paint? Anybody know anything about this?

 

[Boatsb]

Underwater metals do not get the same treatment as the hull. It must be primed to prevent electrolysis with the paint. Look on the manufacturers web site for the full explanation and the recommended barriers.

 

[thoward]

I'm with Scott! We used Interlx 2000, but there are other products.

 

[sgharford]

Grazie!

 

[fixin-to-cruise]

I've had great success with Interlux 353 Viny-Lux Primewash Base which is sold in a kit with 354 Viny-Lux Primewash reducer. It is a "Self-Etching Metal Primer", see http://www.yachtpaint.com/usa/. It has zinc chromate and sticks really well. I have used it on shafts, rudders and trim tabs. You can pre-rinse with some muriatic pool acid. Coating with Interprotect epoxy primer after that would be best before applying the bottom paint.

There is no electrolysis issue with stainless or bronze rudders from antifouling paint. An aluminum outdrive or outboard would have a serious corrosion issue if it were painted with a copper based paint - the active ingredient in most antifouling paints.

 

[REBrueckner]

Follow the instructions for your bottom paint....or e-mail the manufacturer....

I am unsure if an ablative type paint is best for rudders,shafts and props...seems like a hard paint would hold up better if you run a lot....

 

[Glory]

The key to remember is that most bottom paints use copper, in high a percent, to fight growth. Copper is a dissimilar metal and is rejected by the silicon bronze rudders, struts, props, and shafts of any material.

I’ve used several methods of prepping the running gear before bottom painting. my favorite is the Interlux metal primer.

I have great things about “Propspeed”, but haven’t tried it.

JM

 

[sgharford]

I'm going to check with yard today to see what they are going to use for ablative paint on hull - pretty sure last we spoke it was an Interlux product. I’ll make sure primer works with paint they are going to use. I ran about 70 hours last season, so think ablative will hold up. I also picked up Prop-speed paint - Wow is that stuff expensive! Two cat food size cans (200 ml - one primer/etcher, the other paint) was over $200! I just had the props repitched, so figured this was right time to paint em while looking shiny and new. Thanks again – Scott.

 

[fixin-to-cruise]

Regarding the statement "Copper is a dissimilar metal and is rejected by the silicon bronze rudders, struts, props, and shafts of any material."

Not true. In fact Silicon Bronze, which is probably what your rudder is made of, is 97% copper and 3% silicon. Most props are Manganese Bronze which is 58% copper and 39% zinc. Nibral props are mostly copper too, with nickel added.

There is also no problem with using copper based antifouling paint on Steel or Stainless Steel, as is in boat shafts. Again, the only real problem is when copper based antifouling paint is used on aluminum. I've used Micron 66 on shafts and struts with greater success than the non-ablatives like Tri-Lux (I think it was). Prep is really important on the struts and shafts. Micron 66 is chemically ablative and has to be in salt water or it will be damaged after about 1 week. Micron CSC is mechanically ablative, works is fresh water too, but 66 has done a better job in my experience.

I've used propspeed 3 times now and it works great but will be removed quickly if you stir up sand by spinning the boat is shallow water. In deep water it should last a long time (2-3 years?). I don't think there's any perfect solution to keeping props clean.

 

[stormchaser]

Question...if the rudder is mostly copper to start with, why would it really need anti fouling? Wouldn't the copper in it keep away hard growth anyway? They sued to copper plate the bottoms of old wooden ships for this very reason.

 

[Brian Degulis]

Regarding the statement "Copper is a dissimilar metal and is rejected by the silicon bronze rudders, struts, props, and shafts of any material."

Not true. In fact Silicon Bronze, which is probably what your rudder is made of, is 97% copper and 3% silicon. Most props are Manganese Bronze which is 58% copper and 39% zinc. Nibral props are mostly copper too, with nickel added.

There is also no problem with using copper based antifouling paint on Steel or Stainless Steel, as is in boat shafts. Again, the only real problem is when copper based antifouling paint is used on aluminum. I've used Micron 66 on shafts and struts with greater success than the non-ablatives like Tri-Lux (I think it was). Prep is really important on the struts and shafts. Micron 66 is chemically ablative and has to be in salt water or it will be damaged after about 1 week. Micron CSC is mechanically ablative, works is fresh water too, but 66 has done a better job in my experience.

I've used propspeed 3 times now and it works great but will be removed quickly if you stir up sand by spinning the boat is shallow water. In deep water it should last a long time (2-3 years?). I don't think there's any perfect solution to keeping props clean.

If you put copper antifouling directly on a steel boat your going to have a big problem. You just built a battery. Granted Aluminum is worse but steel must be insulated from copper paint it's done with epoxy mastics. All bronze fittings must be insulated from a steel hull also. As far as the rudders go on them it's less about insulating and more about adhesion. Antifoulings don't adhere very well to metal. Idealy your rudders should be abrasive blasted then coated with an epoxy mastic. When the mastic is dry BUT NOT CURED the antifouling should be applied. You can do a thumb print test on the epoxy. If you press on it with your thumb you should leave a print in the paint but no paint should transfer to your thumb.



Brian

 

[Walter P]

Dave's comment about rudders and props being mostly copper based alloys make sense to me. Why should we need bottom paint on them if copper is the active agent in bottom paint and the surfaces being protected are mostly copper? Well something doesn't make sense, there has to be a lot more to what's going on.

We tried Propspeed on a friends 43 DC a couple of years ago and after 2 full seasons, the results were awesome. All the coated running gear was "bug" free. As I see it however there are a couple of drawbacks to it. One thing about it is that it costs quite a bit for such a small amount. The second thing is that the application schedule and preperation must be followed to the letter otherwise you can expect failure. Both problems are probably minor as the time and cost savings of multi-year protection far out weigh the negatives.

Walt

 

[Maynard Rupp]

Down in good old shallow Florida I am told that Propspeed does not last. I guess that in shallow water our props pick up bottom sand. The propspeed folks are unhappy that most of it was gone in a single year. Maybe their prep was bad, but they blame the shallow sandy bottom.

I thought that our brass struts and rudders would stay clean by leaving them bare and sanded to a shine. I was wrong, the barnacles love those brass parts. This time I sanded all the crap off and painted with Petit Trinidad Pro. I don't know if the paint stayed on or whether it reacted mith the brass. I don't dive and our diver doesn't say anything negative. I will find out next winter eh?

 

[sgharford]

This is all great info. Have another question regarding rudders. I used a grinder to get off 28 of 30 years worth of paint from rudder, then a DA sander to get rest. Still have some spots of paint on rudder that are really a bear to remove. Found the silicon bronze sands pretty easy with 100 grit on a DA sander too - fell like I am taking more bronze off at this point then paint. Can I use a paint stripper on silicon bronze or am I just asking from trouble? Any other suggestions from removing those last bits of paint?

 

[fixin-to-cruise]

If you put copper antifouling directly on a steel boat your going to have a big problem. You just built a battery. Granted Aluminum is worse but steel must be insulated from copper paint it's done with epoxy mastics.

Brian

Quoting from Interlux (Akzo/Nobel), the largest paint company in the world...


"FAQ - Antifouling

Question Can I use a copper oxide based antifouling on my steel hull?

Answer Yes, for your steel hull, if you are not over coating an existing antifouling, you will need to apply the necessary Interlux primer. For a one part system, we recommend that you use Primocon. For a two-part system, use Interprotect system. For details of the number of coats you will need, the estimated project time and other details, you should refer to the quick reference Handy Specifications tables in the Boat Painting Guide. "

http://www.yachtpaint.com/usa/faq_online/faq_full_list.asp

Where did you get your info? I am a Hatteras fiberglass hull owner and speak about bronze,stainless and fiberglass from that experience. My steel hull info is just from internet.

 

[Brian Degulis]

Quoting from Interlux (Akzo/Nobel), the largest paint company in the world...


"FAQ - Antifouling

Question Can I use a copper oxide based antifouling on my steel hull?

Answer Yes, for your steel hull, if you are not over coating an existing antifouling, you will need to apply the necessary Interlux primer. For a one part system, we recommend that you use Primocon. For a two-part system, use Interprotect system. For details of the number of coats you will need, the estimated project time and other details, you should refer to the quick reference Handy Specifications tables in the Boat Painting Guide. "

http://www.yachtpaint.com/usa/faq_online/faq_full_list.asp

Where did you get your info? I am a Hatteras fiberglass hull owner and speak about bronze,stainless and fiberglass from that experience. My steel hull info is just from internet.

I've been building steel boats for 25 years. Take a better look at what I said If you put cooper antifouling directly on a steel hull your going to have a big problem. I said the steel must be insulated from the copper paint with an epoxy mastic. What did the paint company say. First prime with Interprotect 2 part epoxy. That's an epoxy mastic. You need to get better at reading the internet!!

Brian

 

[Walter P]

Brian,

In your professional experience, just how thorough do I have to be in removing the old paint from my underwater running gear before applying the 2 part epoxy? As I posted earlier, Propspeed worked for my friend but the preperation was a bear that I would like to avoid. If I could clean it off fairly well and coat it well what are my chances of avoiding "bugs" this season.

The thought of going through all this work and have it fail if bad enough, but then it could get worse, as I would have to remove all the epoxy again.

Walt

 

[fixin-to-cruise]

Missed that detail...I thought everybody had the sense to use primer. Copper based paint would be bad on a Hatteras also in that situation!

 

[fixin-to-cruise]

Getting back to the main question... I'd remove most of it if you plan to go with the metal prep. If you had a problem with the paint adhering, remove it all. If it was sticking well, then 90% is fine. The best paint stripper I've found is called "Aircraft Remover AR-343" from "Kleen Strip".

http://www.kleanstrip.com/

This stuff is nasty, burns skin and should be used with a respirator, but works much better than any other. It will remove imron and Awl-brite too. Get some rubber gloves, a scraper and coarse steel wool pads. There will be zero paint left.

 

[Brian Degulis]

Missed that detail...I thought everybody had the sense to use primer. Copper based paint would be bad on a Hatteras also in that situation!

That's true because adhesion wouldn't be good. But on steel the problem is much more serious than adhesion. The primer must electricaly insulate the steel from the copper paint or you will see severe electrolysis.

Brian