Tin and barnacles?

[hellosailor]

While I was bashing barnacles off a prop today, I started to wonder...will those damn critters grow on TIN itself? Would rigging a sheet of tin under the prop on boat while it was moored (sort of a slobber cup<G>) release enough tin into the water (fairly still) to repel or kill barnacles within a few inches of it?

And of course the converse...does the EPA prohibit parking tin under a boat? (Not paint, just parking a piece of tin tself in the water.)

Would the tin screw the hell out of zincs and copper bottom paint through galvanic reactions?

[Alan Wheeler]

I honestly don't know if it would work, nor legal ramifications of the use.
But Firstly, where do you get a piece of Pure Tin from?? Pure Tin is not the tin in a tin can.
Secondly, I doubt that it would release enough of it's self to affect anything at distance of even a few inches. But it may work if it was "plating" itself to your prop, but you don't want that. Which brings me to the final point of, yes it will react with other metals of difference in Nobility. How much so, depends on how far apart they are on the Nobility scale. Tin in Antifoul was a different animal (TBT). It was released in a controlled rate from the anti-foul binding agent, just like copper, to maintain a surface rich in Tin.

[svChezFreddy]

Down in the Caribbean, a lot of people put a plastic bag around their propeller while moored or docked for long periods. It stops the barnacle growth. Some people remove them before they leave while others go with "the prop will shred the bag" technique.

[hellosailor]

Thanks, Wheels. I figure somewhere out there, someone is selling tin as sheet or ingot stock, no? I know TBT isn't just tin, and copper paints an't just copper...but isn't copper sheeting also being used (since copper bottom days) because the critters don't like to camp on it?

Freddy, the plastic bag idea works for me. Heck, even a biodegrable paper bag <G> but I'm too far north for comfortably hopping under the boat except for a short part of the year. And even then, often don't care to spend time in the water without at least a rinse & delay.<G>

[Alan Wheeler]

I doubt anything would grow on pure Tin. I guess you could get it in Ingot form. Maybe melt it over the Prop seeing as it has a low melt point;-) Nah better not. Not sure what would happen to the prop.
One thought I alwasy wondered though, what about those really tenacuose Grease like anti-sieze substances. International has a product called Res-Q-Steel. It's a copper rich product that sticks like the proverbial and we used it a lot of boat winch cables that lay in the water all the time. Never had one cable rust for years and years in and out of the water. It's amasing stuff. I know it won't last full time on the prop, but I think it would stick on far longer than some sticky things suggested. Plus it doesn't give off an oil slick and it can be applied under the water. Just wear a glove cause it is really really hard to wash off.

[Pblais]

Metalic tin is not immune to marine growth. Pure copper isn't that great either. Once combined with other compounds however it forms the stuff we all know as effective. I think your amature chemistry is leading you away from the target.

[hellosailor]

Thanks, Wheels. I don't really trust any kind of 'grease' to adhere to a prop that's used much.

Paul, I suspect you are right but I had to at least ASK. I know, I'm not the first person to bemoan the fact that barnacles aren't even worth eating...even the French don't harvest them for dinner.<G> Now, if it was bay scallops growing on the prop, I'd happily be in the water all the time!

So I guess a ratty old canvas "belt" saturated with bottom paints and snugged up over the prop would be the thing to try. Maybe this season instead of applying the rest of the paint to the bottom, we'll save some to make a mess on a pit of canvas and try that next season.<G>

Sometimes I feel like a dog looking at an elevator. I know there's a way to make the thing work...it just eludes me.<G>

[jimisbell]

I was just going to start a thread on this subject but this one looks like its appropriater to add to.

I have an 18" bronze prop that I just had re pitched from 18 to 14 and its all shiney etc. I asked the prop shop how I could polish it to a nice smooth shine to maybe discourage oysters and barnacles.

The answer was, "You dont have enough metal there to be doing any polishing, I was even afraid to do any sanding on it."

Then someone suggested getting some one to do a flame deposition of bronze to maybe a depth of 10 mills to build up the amount of metal. Then I thought why not copper so it would be anti fouling and since bronze contains copper it should be compatable. The discussion went on and the suggestion was why not electroplate copper on the bronze prop. At this point I called some shops and found this is easy and cheap.

Now the logic behind this is that the shrimp boats around here use copper pipe for keel coolers and it stays realatively clear of growth. Those same boats have bronze propellers so electrolosys must not be much of a consideration. Bronze contains copper so plating it should be compatable.

OK, now why is this not a good idea? And why do they tell you not to use copper bottom paints on the prop or is that just not on an aluminum outboard prop where I can see there would be an electrolosys concern.

[yotphix]

Cool idea Jimi. Let us know the results in a year or so. If anyone wants the tried and true though, you will find it here.
http://www.propspeed.com/
It is fairly expensive but a Pint kit would do a couple of treatments on a saiboat prop and shaft. A treatment would likely last a couple years though if you are hauling annually to bottom paint i would repeat.

[hellosailor]

Phosphoric acid (a standard acid etch prep), zinc chromate primer (a standard primer) and then something unspecified that is in a xylol solvent as the active top coat.

But after two years apparently not in the US market yet, not much use to us over here.

Jimi, I would think questions about cavitation boiling off the coating at the edges of the blades might be one issue. Then that could leave the edges open to galvanic action between the different metals. Dunno if that's likely to be a real problem, depending on prop speed and metals and how well your zincs are doing.

If you do use electroplating--make sure it is a good plating shop so that bond is good.

[Pblais]

Phosphoric acid (a standard acid etch prep), zinc chromate primer (a standard primer) and then something unspecified that is in a xylol solvent as the active top coat.

But after two years apparently not in the US market yet, not much use to us over here.

Well it's not the first product to come along with the claim that it is slippery enough to repel growth. The pretreatment products are the same old same old. Not much has ever lasted very long and actually worked before. It seems more like this one won't work well either.

The money to be made from such a product that did work and was non toxic is like the golden goose. Sure would be nice if it was real.

[swagman]

A variation on the plastic bag which cold be used when moored in colder climates is a simple 'nappy' that can be lowered over the stern and with a line on each corner, walked forward and tied so the prop is covered. A small handful of swimming pool chlorine dropped inside this 'nappy' once in place will stop any growth on anything.

Have seen several yachts with zero antifouling kept in a bigger version sewn and set up in their pens, and once parked up they simply lift the aft skirt, dosing the trapped water with chorine, and the bottoms still nice and shiny when they come back a month later.

Cheers
JOHN

[jimisbell]

I just got back from the prop shop and they say the 19x18 that I just took off the boat isnt worth repitching so it will become a coffe table ornament. They are selling me a 18x13 refurbished for $275 so that is what I will put on the boat and the recently repitched 18x14 will go in the engine room for a spare.

I checked out the Propspeed stuff and found that West Marine has it for $200 for the smallest can, 200 ml. Which should make two treatments. It sounds good, BUT I just bought a prop for a little bit over that!


I am going to try some of these ideas on anti fouling the prop using my "ornament" prop hanging in the canal with different substances on each of the three blades to get a comparison. Of course that wont test the durability of the coating under power.

[swagman]

I was taught long ago to really polish up the bronze to a shine and then simply cover with an indelible black marker pen. It looks sad coving up all that shiny stuff with black scribble but I always do so and my own prop does not (often) have any barnacles attached a year later.

I'm really not sure just the good polish might not get the same result - but if you've a blade spare to try this - on I'd love to hear the comparative result.

Cheers
JOHN

[jimisbell]

I am getting enough options that I think I will do each side of each blade so that will give me 6 different tests I can do at once.