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Old 03-10-2016, 01:32 PM   #1
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Bottom paint and bonding questions

Hello,

I'm in my second year of ownership but really just my first one not farming 100% of the work out. Attempting to think for myself and understand what "the right way" is vs "the way everyone tells you to do it" and ensuring I'm on the right part of that fork. I've been working all these points myself for some time and have come to obstacles to moving forward for most of these. Certainly there is information "out there" on all of this but the vast majority is lacking any connection to specific cause/effect motivation. Hopefully it's not a mortal sin to collect a number of questions under a single post.

So... in no particular order. Breaking the following sections up so I can spread them over the appropriate sub-forums.


BOTTOM PAINT

1. I've got Micron CSC on my hull and except for 2 square inches, it's in good condition. I spoke with a gentleman at Interlux support who said I didn't need to sand it per se but merely to "rough it up". Is a palm sander overkill? I'm in that "used up" part of my life and machinery does make life better. If not a sander (I'm rich in 80 grit pads btw), then what might you suggest?

2. Order of operations - zincs and paint. I see advantages to doing it both ways but will probably put the zincs on first and delicately cut in around them as I paint... is this anti-stupid?

3. Paint interaction with bonding system - a paint with copper in it sounds as though it has the potential to interact with the bonding system. Any considerations here?

4. While I've been warned away by friends from doing this because of "looks", I'm thinking of doing two coats over the dark blue paint on there now. First a red layer (1 gal) with deployment priority to the high-wear areas, going as far as the gallon will go. Then using applying dark blue (sounds like 1.5 will handle completion). The idea being to have an obviousness when paint wear has moved to an actionable level. I'm sure I'm not the only one that has thought of this but then.. my idea for the V8/6/4/2 engine was later proven to suck to the moon by Cadillac saving me considerable personal embarrassment from my high school mates. So... anti-stupid or am I missing some basic fact and should just do it all one color like everyone else?

ELECTROLOSYS, BONDING AND GROUNDS

As I'm trained in electrical engineering, I find the myriad of things that can screw you royally under this subject fascinating... how the sets of best practices for the various domains (shore, boat AC, boat DC, bonding, signaling, etc) must all coexist sans significant pathologies.

1. They say "check the bonding system before you paint". Is there some particular pathology that drives this point? Check the totality for perfect functionality? I've been searching for a system check procedure that I can accept (i.e. a cause/effect connection to specific faults I want to discover and correct) but mostly all I find is hand waving that falls into the "the way everyone tells you to do it" bucket. Suggestions/pointers deeply appreciated.

2. If I understand a basic principle for mitigating vulnerability to electrolysis, it is that if one can isolate a metal in contact with sea water that that is preferable to bonding it and expanding the number of places a failure can occur. So... my skeg and rudder appear to be isolated from anything else in my boat (assuming hydraulic fluid is a poor conductor). Why would they bond it? Why would they put zincs on it? It isn't connected, or at least seemingly so.

3. There's a brush in the engine room bonding my prop shaft. There's not quite 1.5" of shaft between my prop and where it enters the boat. I can turn a little bit of a 1.5" zinc off on my lathe and make it fit. Do you see any problems with adding a zinc upstream of the prop on an already bonded shaft? Do I need to ensure I put another at the end of the prop shaft somehow?

4. I've pulled a few engine zincs and find I have teflon tape on the threads. Is that not self-defeating?

4a - Corollary to previous - my "on land/dirtbike" skills have me as an aggressive user of loctite (non-perm) on ANYthing that vibrates and NeverSieze on dissimilar metals I to want to later remove without needing a cutting torch. I've had to re-examine these habits shipboard and find more thought is required on every single fastener. I've discovered Tefgel as something that has its place (e.g. steel bolts holding my aluminum windlass cover down). Does Loctite have a role in vibration mitigation? Is there a marine substitute I should use instead? Ditto for NeverSieze, though, my (low certainty) reasoning tells me I'll make things worse using it via electrolysis. I REALLY want to use it on the shafts that my raw water impellers mount on but I'm hesitant that some failure mode I should have seen is just waiting to screw me up good.

5. I discovered during the winterization that the basket in my AC raw water strainer is eaten a smile into itself on the very bottom. I am assuming electrolysis rot. My intent is to braze some SS perf over the hole (I have a friend's throw-away strainer)... it's sort of like the NeverSeize thing... am I creating an electrolysis vulnerability by adding brass?

6. Adding a galvanic isolator.. I'm convinced of the goodness. Can someone recommend a physical location in an NT42 to effectively mount one?


Again... apologies if multi-topic posts are looked down upon. Any contribution to enlightening me on any of the points above would be sincerely appreciated.

Gilhooley
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Old 03-10-2016, 01:54 PM   #2
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Good ablative paint such as Micron CSC doesn't need ANY sanding between coats if it has been in the water even a bit and pressure washed well. At the most a quick hit from 80 grit by hand as fast as you can do the hull would be overkill.

Put your zincs on first or don't...only 2 things are important...the get a good electrical contact with what they are protecting and don't paint but a tiny bit over their edges. if you paint first...you could wind up with a thick enough layer of paint that the zinc might have difficulty making even contact when tightened down. If your friends are worried that a little pain on zincs is a cosmetic issue...they need a life.


No Teflon tape on engine zincs...not required. If your brass plugs wont seal...get another...and snug not breaker bar tight is all that's needed.
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Old 03-10-2016, 02:28 PM   #3
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here we go ... an electrical engineer using the term "electrolysis" and "electrolysis rot" in regards to corrosion. I give up.
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Old 03-10-2016, 02:52 PM   #4
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here we go ... an electrical engineer using the term "electrolysis" and "electrolysis rot" in regards to corrosion. I give up.
But you do have a propane channel following........don't give up, just get a TF guru lobotomy...
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Old 03-10-2016, 03:42 PM   #5
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here we go ... an electrical engineer using the term "electrolysis" and "electrolysis rot" in regards to corrosion. I give up.
Actually, he said "electrolosys".
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Old 03-10-2016, 03:43 PM   #6
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Old 03-10-2016, 03:48 PM   #7
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Actually, he said "electrolosys".
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Old 03-10-2016, 03:55 PM   #8
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Got rid of the hair on my chin and ears so don't make fun!!!!
Oh, I like the ear part of that. Good idea. Do they give a volume discount?
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Old 03-10-2016, 04:39 PM   #9
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I have his book on diesels and got much out of it... thank you.
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Old 03-10-2016, 05:34 PM   #10
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BOTTOM PAINT

1. Fix the bad spot and just paint the rest. You shouldn't have to sand the whole bottom

2. Either/or.

3. No issues unless you have an aluminum boat.

4. Many people do the same.


ELECTROLOSYS, BONDING AND GROUNDS

1. Do some more Googling. The answers you want are out there.

2. If they do not show issues now, you could leave them alone or bond them. If you bond them keep an eye on them after you do it.

3. If there are no issues now I'd leave well enough alone. You don't want to block the path of water getting into your shaft bearing.

4. Yes and no. There should be no need for the tape. But if applied properly it shouldn't cause a problem.

4a. Yes, both the standard Loctites and Tefgel have their place on a boat. As far as "NeverSieze " goes:

http://www.bostik-us.com/sites/defau...nersChoice.pdf

5. Get a new basket or glue the perf on with say JB Weld if you must.

6. As to the galvanic isolator question, I'm not sure what you mean about finding the best location for it to be effective?
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Old 03-10-2016, 08:56 PM   #11
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Without slogging through the whole thing here are a couple:

Quote:
2. Order of operations - zincs and paint. I see advantages to doing it both ways but will probably put the zincs on first and delicately cut in around them as I paint... is this anti-stupid? Not at all, that's how any good yard would do it. You want the zinc to have full contact with the metal it is protecting

3. Paint interaction with bonding system - a paint with copper in it sounds as though it has the potential to interact with the bonding system. Any considerations here?
Not if the bonding system is intact. Here is what can hapopen when it is not:



Quote:
4. I've pulled a few engine zincs and find I have teflon tape on the threads. Is that not self-defeating?
No. The head with the threads is not part of the "zinc" protection. In most cases, actually you can buy a zinc peice that fits into that head without having to buy a whole new assembly. You actually want that isolation, btw, and definitely want the sealant tape or pipe dope, like any other screw in plumbing fitting.
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Old 03-10-2016, 09:22 PM   #12
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No , absolutely not. You do not want or need the engine zink isolated. How would that even possibly work. Hopefully the OP, being an electrical engineer, has enough intelligence to understand why. As for the bottom, just pressure wash and recoat. If you do decide to sand/abrade get a good resperator and some tyvek suits. Or be ready to spend a few days in bed with lung congestion.
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Old 03-10-2016, 09:22 PM   #13
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Greetings,
Mr. c. "The head with the threads is not part of the "zinc" protection." Um...it IS part of the zinc protection circuit and thus MUST be connected (electrically) to both the zinc anode AND the body it is protecting.
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Old 03-10-2016, 10:13 PM   #14
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My understanding too...but whatever is done, as long as there is zero resistance you are good to go.
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Old 03-11-2016, 06:30 AM   #15
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Quote:
Originally Posted by Gilhooley View Post
5. I discovered during the winterization that the basket in my AC raw water strainer is eaten a smile into itself on the very bottom. I am assuming electrolysis rot. My intent is to braze some SS perf over the hole (I have a friend's throw-away strainer)... it's sort of like the NeverSeize thing... am I creating an electrolysis vulnerability by adding brass?
The strainer basket on an AC raw water pump corrodes more quickly as a result of much higher hours of water flow per year as compared to the engine raw water system. Groco makes a plastic (it may be nylon) strainer basket for their strainers. While I prefer good quality stainless stuff, this is an area where plastic is really a better product. Replaced mine with the plastic one ($20?) and have been very happy so far. If you plan to repair or replace with stainless, fasten a zinc on the inside of the basket as a sacrificial element.

Ted
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Old 03-11-2016, 10:19 AM   #16
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Quote:
Originally Posted by caltexflanc View Post

No. The head with the threads is not part of the "zinc" protection. In most cases, actually you can buy a zinc peice that fits into that head without having to buy a whole new assembly. You actually want that isolation, btw, and definitely want the sealant tape or pipe dope, like any other screw in plumbing fitting.
George... You might want to recheck your answer.
Isolated "zincs" or any anodes provides NO protection to the more noble metals
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Old 03-11-2016, 02:18 PM   #17
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Thank you Captain. Might I dig slightly deeper on a few points below...

Quote:
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ELECTROLOSYS, BONDING AND GROUNDS

1. Do some more Googling. The answers you want are out there.

3. If there are no issues now I'd leave well enough alone. You don't want to block the path of water getting into your shaft bearing.

5. Get a new basket or glue the perf on with say JB Weld if you must.

6. As to the galvanic isolator question, I'm not sure what you mean about finding the best location for it to be effective?
1. I've dug deeper on that that I would for many things and what I find is less than satisfying... so riddled with things that are patently false or inappropriate that you can only assume many are just parroting things they heard on the web.... my second bucket: "the way everyone else tells you to do it". I know what continuity is.. I know what voltage is.. I know this system interacts with at least 3 and as many as 5 other similar flavors of grounds to prevent pathologies that frankly aren't part of everyday life in electricity as I work with it. There is this remark... CHECK BEFORE YOU PAINT. Ok.. I take that at face value in case there's a good reason inaccessible to me, because that is prudent... but statistically... frequently I'm thinking it's probably just noise from a guy who ought to stick to what he knows. Seriously.. there is SO much bloody bad and even dangerous information, not just on line but falling out of the heads of the guys who call themselves professionals at the boat yard. Just plain wrong. I'd get sued into the stone age or die from shame if I worked at their typical level. That's background on my frustration with the quality of information in the marine industry/web/verbal crap you hear at the dock.. not a lecture at all. It's why I think I've hit a wall on this since if there were a good resource on this (e.g. Peggy Hall's drinking water post) the entire world would know about it. If you stumble upon such a well-justified/explained procedure someday I would dearly appreciate a pointer to it. Thank you.

3. Not a question... that is really sharp thinking... I never considered the water supply. THANK YOU.

5. I can do both of those things.. and also braze... brazing is actually the fastest for me if you subtract out the time I'm spending harassing the good people here. Is it the case you have a specific reason you don't support that approach? Corrosion? I have applied so much JB Weld to machines on the sides of trails over the years.. I have it on the boat and in my cars but I do dislike that stuff enough that it has never made it on to my list of things I use for permanent repairs. Keeps the oil in a crank case long enough to get back when you screw up in the rocks

6. I remember adding the word "effective" as I typed that thinking I was doing a good thing. I'm sure you know better than I that it goes between the shore power port and the AC panel. Was hoping someone knew NT's well enough to suggest the best place. I haven't grown my chops in terms of tearing into walls yet.


To the others who also posted replies, I'll say thank you here.

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Old 03-11-2016, 02:23 PM   #18
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The strainer basket on an AC raw water pump corrodes more quickly as a result of much higher hours of water flow per year as compared to the engine raw water system. Groco makes a plastic (it may be nylon) strainer basket for their strainers. While I prefer good quality stainless stuff, this is an area where plastic is really a better product. Replaced mine with the plastic one ($20?) and have been very happy so far. If you plan to repair or replace with stainless, fasten a zinc on the inside of the basket as a sacrificial element.

Ted
Sounds like I'm 0/2 on the brazing idea... both politely and knowledgable articulated. DEAR GOD do I hate not fixing my own stuff! I'll take your suggestion for a zinc and run with it. Thank you.
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Old 03-11-2016, 03:23 PM   #19
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Corrosion Reference Electrode Product Specifications
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Old 03-16-2016, 10:46 AM   #20
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Finally got some time to do the braze.. despite first doing some practice work on similar gauge SS perf, it was disgusting though it would hold. I do fine on heavier stuff but not on this. Yet another skill no where near where it needs to be. Plastic order going in after I type this.
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