Advice for Corrosion

General boating discussion
BCTony
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Advice for Corrosion

#1

Post by BCTony »

I wonder if I may ask advice of the experts here.

My boat is a 24’ North River Seahawk Offshore almost four years old. It is bare aluminium but because at the time of order I knew nothing of mill scale corrosion it has not been acid washed. The boat is moored year-round in saltwater.

Ever since taking delivery of the boat I have been plagued with leaks. Water leaks through windows and most particularly leakage from the self-bailing deck into the bilge. In addition to steering hydraulic leaks and fuel leaks! To a large extent North River have been helpful but because of the distance from my home in Canada and their factory in Oregon it has not been possible to return the boat to the factory as frequently as the problems would have required. North River have been pretty good in authorising local marine shops to make repairs but this proved disappointing for both North River and myself. There has been some bullshit along the way such as ‘probably the water you’re seeing in the bilge is condensation’. Yes –right, a gallon of water in the bilge after a night of rain!

Persistence and being a PIA as well as too some extent throwing money at the issue by paying to have the boat transported back to Oregon, I have now almost resolved all issues. Eureka! The only thing that is leaking now is a Freeman hatch on the engine pod and I am just waiting for some decent weather to change the seal when I am confident this leak can be resolved. Until the next appears of course!

I am neurotic about corrosion and I have done everything to keep the bilge free of water through vacuuming out all water on a regular basis. But I am worried about corrosion that may have got started. One of my in-deck fish boxes has corrosion.

While at North River late last summer they had the fuel tank out. Speaking to one of their employees on another matter, it was mentioned ‘I was asked to look at a boat we had in – it might have been yours – and there was corrosion there’. Oh great! Of course I have now convinced myself that it was my boat!

With the fish box I put a gallon of vinegar in for a day which seemed to clean everything up. I rinsed thoroughly and also added some soap. However, I have noticed in recent weeks during the colder months that signs of corrosion seem to be returning – please see photo.

Looking into the bilge through the engine pod hatch I cannot see any signs of obvious corrosion. Photo attached. I keep it as dry as possible through vacuuming but seldom is there absolutely no water A few months ago, I also swilled this for a day with vinegar and afterwards flushed with freshwater and added soap.

The principal area of leakage of water from the deck into the bilge was the fuel tank pad. North River remade this last summer and for the first time it does not leak. I am therefore reluctant to have anybody remove the pad and then fuel tank to inspect the bilge.

As I say the only area where I am sure there is corrosion is in one of the three in-deck fish boxes.

I would be very grateful for any advice you can offer. The only obvious area (to me) of corrosion is in the one fish box. Asside from the aggravations mentioned, I love this boat and want to keep it for many years.
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Re: Advice for Corrosion

#2

Post by Aluminum Clone Owner »

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BCTony
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Re: Advice for Corrosion

#3

Post by BCTony »

Yes - I do have shore power and I do have a galvanic isolator. I also have had the readings on and surrounding my boat tested and everything is at should be. I am surprised by your 'Wow' reaction - are you seeing definite signs of corrosion other than in the fish-box? What I am saying is that I am not sure I can correctly identify corrosion.
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Re: Advice for Corrosion

#4

Post by Aluminum Clone Owner »

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BCTony
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Re: Advice for Corrosion

#5

Post by BCTony »

I think there is pitting in the fish-box. I do not think there is pitting in the bilge - but please tell me what you think.

Yes - the boat is moored all-year in saltwater. When moored it is connected to shore-power with galvanic isolator.

I have aluminium anodes and an ElectroGuard Monitor fitted. The monitor reads in the over-protected range when moored with engines 'up'. With engines down the monitor reads in the 'safe' range. It was because of the over-protected reading I had the electrical readings checked in co-operation with ElectroGuard which were all found to be in the acceptable range. I have been given to understand that you cannot have too much aluminium anode (unlike too much zinc anode). Thank you for your information.

You see that I have an anode in the bilge. I am beginning to think that perhaps the fish-boxes should also have an anode.
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Re: Advice for Corrosion

#6

Post by BCTony »

This is the report 05/10/2016:-

TEST HULL POTENTIAL
SERVICE CALL TO THUNDERBIRD MARINA SLIP C-14
ELECTO GUARD MODEL 125A IS READING INTO THE OVER PROTECTED ZONE ON THE METER
TEST HULL POTENTIAL TO CONFIRM HIGH READINGS ARE DUE TO ALUMINUM ANODES AND NOT ACTUALLY OVER
PROTECTION
CONFIRM POTENTIAL IS NOT BELOW -1100mv (POTENTIAL OF ALUMINUM ANODES)
TEST AND RECORD POTENTIAL
1) AS BOAT SITS IN MARINA WITH ENGINES UP AND SHORE POWER CONNECTED
2) WITH SHORE POWER DISCONNECTED
3) ENGINES DOWN W SHORE POWER CONNECTED AND DISCONNECTED
4) DOCK POTENTIAL
INSPECT FOR AND EVALUATE ANY OTHER CONCERNS WE HAVE
- CALL TONY TO MEET US AT THE BOAT
- CALL TED SCHWARTZ AT 1-530-926-4000 PRIOR TO GOING TO ENSURE HE IS AVAILABLE FOR CONSULT BY PHONE IF
NECESSARY
Description:
TEST HULL POTENTIAL
RESULTS:
1) AS BOAT SITS IN MARINA WITH ENGINES UP AND SHORE POWER CONNECTED -1.082V
2) WITH SHORE POWER DISCONNECTED -1.082V
3) ENGINES DOWN W SHORE POWER CONNECTED AND DISCONNECTED
-1.052V ONE ENGINE TILTED DOWN
-1.003V BOTH ENGINES TILTED DOWN
-0.993V BOTH ENGINES AND KICKER TILTED DOWN
4) DOCK POTENTIAL -0.843V
Resolution:
HULL POTENTIAL READING ALL IN RANGE
UNDERWATER METAL IS ALL ADEQUATELY PROTECTED AND BELOW THE OVERPROTECTED RANGE
GALVANIC ISOLATOR IS INSTALLED AND WORKING PROPERLY
RECOMMENDED 120V A/C SHORE POWER UPGRADES
1) INSTALL NEW BREAKER PANEL WITH MASTER 2 POLE BREAKER AND REVERSE POLARITY INDICATOR
2) INSTALL PROTECTIVE COVER BEHIND BREAKER PANEL
Last edited by BCTony on Mon Feb 13, 2017 12:17 am, edited 1 time in total.
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Re: Advice for Corrosion

#7

Post by Aluminum Clone Owner »

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Re: Advice for Corrosion

#8

Post by BCTony »

Do what - install an anode to the fish-box(es)?
Not intending to be rude just seeking clarification.
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Re: Advice for Corrosion

#9

Post by Chaps »

Hi Tony,
Is that pitting or just oxidation? (my whole boat looks like that!) Could be moisture having its way under mill scale too. I'd get some commercial grade vinegar and slosh some in there, let it sit for a few days then rinse out. see if it cleans up. Bare alloy looking scroungy is in its DNA. You could attach something like a trim tab anode in there and see if the anode starts to react, if you can't get to both sides of the box to attach a nut for an anode drill a smaller hole and tap it. They are usually 1/4-20 or 5/16-18 bolts that come with the anodes. Of course you know to use aluminum anodes.

Been fishing? Did you do the derby in the SJ islands?
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BCTony
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Re: Advice for Corrosion

#10

Post by BCTony »

Thanks Bob - I was hoping either you or Kevin or both would comment. Referring to the fish-box I don't think its oxidisation. If I touch or rub the 'pinnacles' they all dust up white powder. The fish-box on the other side and the big centre fish-box do not look like this and are just smooth tarnishing aluminium. It has been suggested that perhaps (!?!) I had fish in the box and did not rinse out properly afterwards. This is very possible because water is 'off' at my marina for too long in the winter. I'll try with vinegar again - I did before just after the boat came back from you - and it cleaned up well but then the pinnacling-powdering has started again. While I have the ingress/exit valves closed water still gets in the fish boxes when it rains; it is not by any means dry storage. If fitting an anode is an answer I think I would prefer to try and have one welded rather than make a hole that could eventually introduce water to the bilge.

Have not fished for five weeks - been back in UK, Europe and NYC! And yes - fished the Friday Harbor Salmon Classic beginning December. Did catch but not well enough to win. A 14.61lb Salmon took $15,000 first prize plus $7,600 side-bet. Not a bad day's fishing! You should come up this December it's a great fun event.
BCTony
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Re: Advice for Corrosion

#11

Post by BCTony »

Well I have left the fish-box to soak for a few days in vinegar. It definately is pitting with pits all over. I guess that after rinsing the next step should be to sand but I would be grateful for any and all suggestions.

It is strange the fish-box on the starboard side is fine and the aluminium smooth although there are some 'swirls' to suggest there might have been some sanding inthe past. Perhaps there was a previous outbreak on that side before delivery to me.
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Re: Advice for Corrosion

#12

Post by kmorin »

BCTony,
I'd like to ask you to consider re-reading some threads here that dealt with the three types of aluminum corrosion? I don't have them indexed or recall the names but I'd say they're worth a look since they're preface to my remarks.

Chemical, galvanic, stray current corrosion(s) each one operates at the metal molecular level to 'corrode' (convert o r transfer metal to some other material) the aluminum. Usually, chemical is from acidic conditions; usually, galvanic is from too close or even contact with another metal;and, usually, stray current comes from electrical power that "finds a path to zero potential" through the hull or its parts.

#1 When the chemical "cell site" acts: the aluminum oxide that 'electrically' bonds to the parent metal and 'defends' the metal atoms from reaction- is removed by the chemical agent and then the chemical reacts with the metal. The transfer/corrosion action is at the "electrical" level of molecular interaction.

Protection is to keep acids and bases from the oxide or replace the oxide with a Chromium oxide (primer) or other oxide (anodizing) that is 'tougher' than native aluminum oxide. Or keep the exposure to all liquids with ph range that aluminum can tolerate without corrosion. http://www.aluminiumdesign.net/design-s ... esistance/ (reference reading on this subject)

#2 When the galvanic site cell acts: the aluminum oxide (protective film) is overcome by molecular level electrical attraction. The transfer/corrosion action is at the "electrical" level of molecular interaction- not from the chemical but from the other metal's molecules' make up of atoms.

Protection is to remove any metal to metal contact with aluminum that could get wet. Most non-conductive materials work -plastics being the most common.

CAUTION, if you use a plastic insulator and that forms a thin film of water under the plastic next to the aluminum you can created a crevice corrosion cell (!!)

#3 When the aluminum metal, underlying the oxide has enough electrical charge NOT at the molecular level but at the DC battery level (!!) the molecules of oxide can be lifted/overcome/breached from a "potential energy" (voltage is potential) inside the parent metal. This can result in a migration of molecules out, lifting the oxide and powering the transfer at a high rate - this means current flows - out and it is carried by the transfer of molecules out of the metal.

Protection, (mentioned above in previous post) all electrical energy (not discussing molecular attraction levels of energy) used on the boat need to be provided low resistance paths from the energy source and back. Two leg wiring circuits and chassis isolation OR bonding wires need to be considered as well.

Don't mean to lecture, all this can be found here, on AAB.com Forum, in other words, and countless of other places online: 99% of those other sources will be better written/explained than I did here.

What I'd like to say is that you're showing a general overall chemical reaction type of corrosion- as I can see from the photos? That implies there is some 'agent' getting into the fish box to mix with the bilge water that is causing a uniform- generalized chemical surface pitting corrosion. This would imply the compartment has some means to contaminate the rainwater?

OR: You didn't use Simple Green as the soap to wash out the vinegar did you? Heavily rinsed it works OK but I have seen some bilge cleaning where the heavy duty concentrated version was used and there was definitely corrosion - not sure what's in it but if you're using this or ANY soap- might look at the MSDS and make sure you're able to rinse - plenty.

Are there copper/bronze/raw rubber (carbon based not synthetic) products involved? all these can create a solution of corrosion chemical soup? The two metals would dissolve into solution (valves, hinge bushings, tubing, fittings?) that makes the entire bilge into a "galvanic solution". Or, if the water is allowed to stand in the bilge for long enough- in a close chamber- and there was only a small volume- could the water become acidic? (ph strips available at your drug store- if they are dipped in your bilge water and show acid- add baking soda to neutralize- not dilute).

Stray current? IF you have stray current problems in a fish box/hold I'd expect to see pits that were A) wide and few B) lined up with the conductor that was bleeding the current- bared wire in the bilge under the deck but outside the fish hold. C) deep pits with a greyish paste and soft metal in a 1" to 2" wide area?

If the pits, when dried, show the white powder and acid/vinegar will clean the surface- but they reform- that implies a film of polluted bilge water is coating the surface, drying or running off, then re-coating during movement of the hull when this solution is present. It sounds chemical but that would look similar if there were copper salts in solution with the bilge water.

Deck seal? path to bilge for rain water/deck wash, organics? (fish cleaning run off?) all these items need to be explored.

Last, is just a shot in the dark? deck lockers/fish holds may not be made from the same higher grade alloy as the rest of the boat? I doubt if the builder uses 5086 (with MTR's) for fish boxes since the 5052 alloys bend much easier with tighter radius and less effort. So.... what if you have a fish box/hold/locker made from some "out of spec." marine alloy? That one locker showing corrosion performance below the rest of the hull's panels and framing makes me ask about the pedigree of the metal?

Not sure I'm any help? I have lots of questions.


Cheers,
Kevin Morin
Kenai, AK
kmorin
BCTony
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Re: Advice for Corrosion

#13

Post by BCTony »

Thanks Kevin. I am not sure if I understand everything properly but I am a reading and re-reading everything I can. It has been suggested to me elsewhere that it might be a difference in alloy grades with a lessor grade used for the fish-boxes or some of them. While the fish-box on the starboard side shows indication that it might have been polished and/or sanded previously (my boat was bought new) it does not show sign of corrosion. Neither does the big central deck fish-box which while I have the inlet/exit pipe bunged almost always has a little water in its 'v'. But there is also a fish-box on the transom that I notice today also has slight pitting to which I have now applied vinegar for a soak overnight.

With the port fish-box in question I have today vacuumed out all the vinegar and rinsed umpteen times. What I noticed was that this 'lathered-up' at the beginning indicating the presence of soap. I have rinsed until everything was clear and then I have hand sanded; more as a test as anything else. The pitting is very extensive like a rash and some are quite deep maybe a 1/16th. I am thinking that tomorrow I shall re-apply vinegar for a couple of days while I purchase a belt-sander.

I shall look at the soap I might have used - but are you able to recommend something that is definately OK? Usually I use 'bilge cleaner' or Sunlight.

In the past I have left the valves to the side fish-boxes 'open' as the table-tennis ball type scuppers have stopped them flooding when boat at rest. However, since the boat was last out of water the scuppers have been failing because they either need cleaning and/or the fixing tightened. The boat has not otherwise necessitated being hauled out for the last five months or so. This has meant that there has not been the regular flushing that would normally occur. So maybe inadvertantly I have allowed some sort corrosive gunk to form. Because what you describe the white powder cleared with vinegar but then reappeared when sections of the fish-box dried out. Some of the problem and problem for its resolution is that the bottom of the side fish-boxes are flat horizontal meaning that a little water sits as a film across the entire surface when the boat is stationary. There is a slight migration aft which of course when the boat is running and the valves open would mean that there is probability of expulsion.

I cannot find anything to indicate stray current from any source or leaching of another metal. The lid of the fish-box has chrome hinges and no doubt stainless steel bolts and there is a rubber type product to seal (which of course doesn't) but no sign in their close proximity to indicate an issue.
jj225
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Re: Advice for Corrosion

#14

Post by jj225 »

This may sound like a dumb question but why don't you pull the boat out of the water? You obviously have a trailer to put it on. Keep it on the trailer for several months and see what happens. IF the corrosion continues then you can go back to NR and talk to them. IF it stops, then you can try to isolate where it's coming from. If it was me, I'd pull that boat out of the water faster than you can type corrosion in this post.

BTW, did NR pay for your gas or cost to have it brought down to them? They should have if they didn't. I had some water issues myself but the builder paid for my fuel RT from So. Ca. to Seattle.
BCTony
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Re: Advice for Corrosion

#15

Post by BCTony »

Thank you for your suggestion. But no - I do not have a trailer and nowhere to store the boat. The whole point of having the boat is to have it in the water in the marina and ready to go fishing. I am interested in fishing not boating.
jj225
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Re: Advice for Corrosion

#16

Post by jj225 »

Oh I just assumed that since you had to get it from OR up to BC and vice versa it'd be on a trailer. My bad. Although it'd be pretty easy to think that you owned a trailer. So I guess NR didn't kick in for the cost of transportation then either? That would suck as I"m sure it wasn't cheap to have to pay someone to put it on a trailer of some sort and take it down to OR and then back up. Two times was it? Not counting the original purchase trip? Bummer. Double bummer for not having a trailer because you could always put it in storage. I mean you do want to see if the problem lies with the boat in the water or not don't you? Because you haven't figured it out with it in the water yet and you're running out of ideas. Just saying.

I too am interested in fishing and not boating. There are some that put hundreds of hours/year on their boat even though it sits on a trailer. I have 350 in about 2 years on mine and that's not even fishing every month either. Don't see your point.
BCTony
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Re: Advice for Corrosion

#17

Post by BCTony »

JJ25 I did not intend my reply to your post to be 'snotty' in any way. I had a trailer with purchase but I do not have a truck and the boat on trailer were too heavy for my SUV. Also I have nowhere to store a trailer. So after a year I sold it. Boat has been back to NR three times now. First courtesy of the dealer (who had managed to install the twin engines at different heights), the second 50/50 with NR and the third at my cost. No - not what I wanted but I have not found a reliable marine shop locally. Despite everything I still think NR are the best to sort out the issues.

I am still a fairly inexperienced boater and I seem to be learning everything the hard way. And I hope I am learning.......... :banghead:

I seem to be getting conflicting advice. Today I spent sanding the fish-box - the pits are quite deep and I do not think I can remove them completely. I spoke with NR who seemed to think that sanding was not a good idea as I am removing the oxidising. I thought this was the idea and that the oxidising self-healing properties of aluminum would re-commence. I have not finished the sanding but now I have started I think I should finish. Certainly on the sanded section the pits do not feel as aggresive and in a lot of areas while 'freckled' it feels smooth with the odd deeper pit.

Generally I fish 3-4 times a week and here in Canada we are not as well served with boat ramps as it seems to me that you are in the USA. Trailering for me is not an option. Perhaps I should have bought a Clorox...........
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Re: Advice for Corrosion

#18

Post by noexcuses2 »

BCTony wrote: Tue Feb 21, 2017 11:05 pm
Perhaps I should have bought a Clorox...........
not unless you like buffing, waxing, gel coat repairs, fiber glass repairs and oh yeh buffing and waxing some more :banghead: :banghead:
BCTony
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Re: Advice for Corrosion

#19

Post by BCTony »

noexcuses2 wrote: Tue Feb 21, 2017 11:47 pm
BCTony wrote: Tue Feb 21, 2017 11:05 pm
Perhaps I should have bought a Clorox...........
not unless you like buffing, waxing, gel coat repairs, fiber glass repairs and oh yeh buffing and waxing some more :banghead: :banghead:
:rotfl: :rotfl: :rotfl: :rotfl:
jj225
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Re: Advice for Corrosion

#20

Post by jj225 »

BC Tony, no worries. I know how difficult it can be to write something and wonder if it came across the wrong way. One can't inflect tone when writing.

As for your boat, it really is a bummer. Even more so w/out the trailer now. I'd still want to get it out of the water and see what happens. I wonder if you could rent one from someone who has their boat in the water and has it sitting around?
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Re: Advice for Corrosion

#21

Post by BCTony »

It is my belief that my issue relates to insufficient housework on my part. In other words that the fish-box became contaminated with saltwater that was not flushed out sufficiently and allowed to dry and/or the little water that gets left in the drainage pipe become acidic. That is the corrosion is completely due to saltwater. I am pretty certain that I can identify when this might have occured. What this experience has led me to conclude that for a boat that is in perpetual moorage such as mine that I must be be more systamatic in my clean-up - I thought that I was but this episode has taught a lesson and I shall instigate a control system to prevent its repetition. I also think it is essential that that I should have pumps fitted to pump-out water and not just an on/off valve as I have at present.

I have soaked the fish-box with vinegar a couple of times, flushed vigorously and now sanded the affected areas - but there are numerous pits. The larger ones I shall clean-out and fill with marine tex. I then propose to acid wash with muriatic acid, neutralise with baking soda and then flush rigorously with freshwater before applying epoxy barrier paint to the bottom panel. If the corrosion re-appears then I shall have the bottom panel cut out and a replacement new panel welded. As of yet I have not noted a similar issue elsewhere.

In fact I am thinking there is good argument for having all the fish-boxes applied with epoxy barrier paint. It has been applied to my anchor locker to help prevent the situation of wet anchor rope causing corrosion in the locker. It seems to me that epoxy offers some protection over bare aluminium. This might be something I shall have done when the boat is next due for bottom paint.

Obviously rigorous washing down after contamination with saltwater is to be recommended but sometimes water is 'off' at my marina in the winter for perhaps two months or even more. This makes things very difficult. I don't know how people cope further north or where there is not freshwater available for washdown.
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Re: Advice for Corrosion

#22

Post by kmorin »

Tony, I would like to review your post to point out what appear to be misconceptions? My understanding of the various corrosion issues we've seen on aluminum boats in general and yours in particular seem to lead me to different conclusions.
BCTony wrote: Sat Feb 25, 2017 1:32 am It is my belief that my issue relates to insufficient housework on my part. In other words that the fish-box became contaminated with saltwater that was not flushed out sufficiently and allowed to dry and/or the little water that gets left in the drainage pipe become acidic.
My understanding is that 5086 and for the most part 5052 (or 5083) will all remain immersed in salt water for "a hundred years" without corrosion- if there are no other sources of corrosion. That understanding comes from seeing 50 year old welded boats without any corrosion in them- except for those places where the three causes of corrosion were formed. Just salt water is not a means to corrode 50series aluminum that I have ever seen or heard about?

Second is the idea that the water could become acidic - I'm not aware of any mechanism to change the ph of the saltwater in an open pipe. My understanding is: #1 the water needs to be in a thin film #2 the water needs to become deareated so open standing water does not do this in a pipe- but might do so in a bucket if left for sufficient time (decades? years?). The key item in deareation as I understand the process is for the oxygen in the water to initially be used to create new aluminum oxide- thus changing the ph? If there is atmospheric oxygen covering the water on one side: there is no mechanism to deareate or remove oxygen as there is plenty in the air?

I don't see how the "ph-shifting mechanism" is present (?) unless the drain pipe is lined with a concentric pipe to allow the water to stand/stagnate/deareate in a very thin layer held in place by capillary action?

The idea that the standing, open to air, salt water can become acidic in the bottom of a fish hold but not on the entire hull, all holds, bilge and every other place- is hard to accept since the conditions don't seem different enough to make a separate circumstance? More likely is the material is defective OR, that fish hold has some contributing factor to make the bilge wash either galvanically active like a metal salt in solution; or corrosively active in ph?
BCTony wrote: Sat Feb 25, 2017 1:32 am It has been applied to my anchor locker to help prevent the situation of wet anchor rope causing corrosion in the locker.
Here you note the fact that the wet rope, against a bare aluminum surface, can cause corrosion! I agree- the rope surface provides a contact and thin film of water! That thin film can become deareated and shift ph- but those conditions (anchor locker's wet rope against bare metal) do not seem present in the fish hold? My current understanding of the crevice corrosion cell is the that robbing oxygen is what shift the ph of the water from neutral to acid- saltwater is neutral ph. So, what mechanism is present in an open fish box bottom panel to convert the ph? I can't see it yet?

Why is it happening in only one hold? What is the difference in use, cleaning, and flooding of the two holds? Why one and not the other? I'm not saying using an epoxy paint layer is wrong- I'm asking you if the evidence supports the ideas you're saying are your current beliefs about the problem?

My post is not to give a hard time, please don't think I believe that I can diagnose your boat from thousands of miles while you're right there!!! My purpose is to point out that my understanding of the mechanisms to widely and uniformly pit - aggressively pit- a fish hold bottom panel while its opposite side mate is not experiencing the exact same behavior; are not upheld by your reports.

You etched with acid (vinegar is just a very mild acid) which would have cleaned some of the existing surface of oxides and would have 'scoured' the corrosion sites to some degree. (the corrosion sites may or may not have been completely etched to their lowest surfaces of pure parent metal?) Therefore this plate/panel has no more mill scale to retain an promote crevice corrosion sites.

What' s left - being flooded with acidic liquid that dries in places (concentrates the acidic "salt"f or residues that could be used to make more acid by adding water). But if you rinse/wash down the tank/hold/locker with any volume of either salt or fresh water the dilution factor would have reduced the ph to an noncorrosive level. I don't agree with your concept that salt water will corrode a 50series aluminum boat.

That still leaves me with the conclusion #1 there is some condition in this location that is not evident -yet. The condition seems to create either an acidic bilge or a galvanically active bilge solution.... O R #2 the metal's original manufacture was not fully compliant with the 50series alloy standards?

Just relying on what's been posted to make these remarks, maybe Chaps or some of the other owners who've had any similar problems can see things I'm missing and give another view that is more helpful?

Cheers,
Kevin Morin
Kenai, AK
kmorin
jj225
Posts: 145
Joined: Wed May 02, 2012 12:36 am
11

Re: Advice for Corrosion

#23

Post by jj225 »

My fish hold will often have wet dock lines and bumpers (saltwater) in there and I have zero corrosion. In fact, I just came from the boat where I'd put water in the hold and let it sit for about a month since it had had one of the dock lines and bumpers with fish gunk all over them. Probably sat for a month before I did that. Pulled the plug and let it drain and I didn't see any sign of corrosion. That hold gets everything from tuna to rockfish in there too. Seems hard to believe that you'd get the corrosion you're describing from lack of proper cleaning. BTW, I clean with just soap and water and sometimes just water.
BCTony
Posts: 103
Joined: Thu Feb 10, 2011 2:02 am
13

Re: Advice for Corrosion

#24

Post by BCTony »

Thank you Kevin and JJ25. You highlight some doubts that I share. I referred the matter to North River who said to me that it looked to be purely saltwater corrosion. Let me run through a timeline of what has occurred. My boat went back to North River end of June and was away far longer than anticipated.

Transporting the boat to North River involved my taking the boat by sea into the States where it was put on a trailer and taken down to Oregon. While the boat bottom was pressure washed the time schedule did not allow a regular wash-down. Shortly before going to Blaine I fished a Derby on Vancouver Island (and won!) where four fish were placed in the fish-box in question but there was not any wash-down facility. It could be that the only wash-down this fish-box received before its extended trip south was from salt-water. This is what I am assuming because I can’t remember.

Prior to its trip back to North River I was not aware of any corrosion anywhere. I was concerned for the parts of bilge I could not see since there had been leakage from the deck from day one. North River remade the deck fuel tank pad and also found a leak in the fuel tank. When I visited North River in August the fuel tank and deck fuel tank pad had been reinstalled so unfortunately I could not see the bilge. This has some significance later in my tale. Funnily enough I did refer to a little brown staining in the main deck fish-box. I was told that aluminium corrosion was white powder and that the slight staining I was referring to was probably from something else I had had in the hold. Which fitted because I had had an anchor buoy in there where the attachment ring was rusting. I did not refer to or look into the side fish boxes because I then had no reason for concern.

I was emphatic that the boat should not be returned to me before they were 100% that the deck did not leak water into the bilge. That I was neurotic about corrosion and that the best way of reducing the risk was to keep all water out of the bilge if possible. The difficulties of keeping all water out of a bilge was discussed and of course it is not easy but if you give up at the first stage of construction what hope do you have. It was suggested that an anode in the bilge would be a good idea as with effective barrier and bottom paint the anodes on the outside of the hull would not protect the inside. In view of which I agreed and you can see the anode in one of the pictures on the first post.

In addition to warranty items, other work I had down at North River were the addition of side rails, epoxy of anchor locker, the installation of a spotlight and an Electro-Guard 125A Cathodic Protection Monitoring System. When all was complete the boat was taken to Chaps who renewed the bottom paint and anodes (an excellent job as far as I can see). I picked up the boat from Chaps and if I had any concern about any corrosion anywhere I would have discussed it with Chaps.

There were two issues when I got the boat back home beginning of September.

First, the side fish-boxes were flooding when the boat was at rest. I discussed this with Chaps who felt maybe he had not finally tightened the scupper fixings when re-fitting. I shut the on/off valves to the fish-boxes, vacuumed out the water and rinsed but the boat has not been out of the water since to look at the scuppers. North River are sending me replacement scuppers in case the existing ones are damaged and I hope to be able to deal with this issue in the next week or so.

Second, the Electro-Guard monitor was showing in the ‘over-protect’ section of the gauge with the boat at rest in its mooring and all engines raised. In fact it was almost far as it could go in the ‘over-protect’ range and with all engines down in the water only retreated to about a third of the way up the ‘over-protect’ range. I should mention that nearby my slip there is at least one creek flowing in so the water is at least a little brackish. Out in the ocean proper with all engines down the reading is between half and two thirds of the way up in the ‘safe’ range. I spoke with North River who said when they tested the boat they noticed the monitor was ‘a bit off’ but that any adjustments had to be made with boat in its regular mooring. This was of course before the renewal of bottom paint and anodes. I then spoke with Electro-Guard who after obtaining assurances that I had not fitted the wrong sort of anodes or mixed anodes decided that a local firm known to them should come along (at my expense) and do tests at my moorage. The result of the tests was posted earlier in this thread on 12/02/2017 and concluded everything was in order. I have aluminium anodes on the boat and engines and it would seem that the Electro-Guard monitor was calibrated for zinc. I have grumbled at Electro-Guard repeatedly about this saying ‘what is the point of having a monitor which reads ‘over-protect’ most of the time?’ Apparently you cannot over-protect with aluminium anodes and Electro-Guard have not suggested that I remove any anodes.

It was shortly before this inspection that I first noticed the puffing-up of white powder in the side fish-box. I put a gallon of supermarket vinegar and left it for a few days before vacuuming out and rinsing thoroughly. It all looked good and clean and I could feel that the vinegar has etched the aluminium slightly. In fact I mentioned this to the technician who did the testing.

Because I kept grumbling at Electro-Guard I suddenly received a call from someone new to me at North River. The purpose of this call seemed to be to settle me down about my Electro-Guard monitor. It was explained that as my bottom paint was new and of the highest specification along with new anodes it would take some time for everything to settle down and for the monitor readings to migrate closer to the expected position on the monitor. The conversation moved on to talk about my boat having been at North River all summer, my anxiety concerning corrosion because of all the leakage into the bilge, my issue with the side fish-box and my (as I thought then, successful) treatment with vinegar when it was said that this person was asked to look at a boat (by the technician who worked on my boat) to see if there was corrosion ‘it might have been your boat, but, I am not sure, it might have been’ and ‘there was some corrosion’. Oh fucking great!

While I corresponded further with Electro-Guard at that time nothing has been recommended. The monitor readings have migrated back towards the normal range but the reading is still about a third of the way up the ‘over-protect’ range when the boat is in its slip with all engine raised. With engines lowered in the slip, the reading is right on divide between over-protect and safe. At sea when trolling with all engines down the reading is in the middle of ‘safe’. I understand that Electro-Guard have a new monitor being launched this year but Electro-Guard have told me that my readings would not be markedly different with the new monitor. I am somewhat disappointed with Electro-Guard and they will be hearing from me further – it certainly is not matching up to their advertising. Nevertheless, everything considered, I do not think I have an issue with cathodic or galvanic corrosion.

To return to the corrosion issue in my fish-box. The above events conclude towards the end of October. In November I was travelling and away for most of the month. When I returned I noticed the re-commencement of mounds of white powder. Very similar to worm holes in sand. This increased as the month went on. It was suggested locally that I had probably left a fish in there and not rinsed out properly and that I should put in some soap. I sloshed a dollop of undiluted ‘Spray Nine’ disinfectant cleaner along with the water that was in the box. (It is green but whether it is Simple Green I do not know – I cannot see anything in the MSDS to raise concern). January I was again away travelling until the month end. When I returned where the fish-box bottom was covered in water looked OK, but, the part that was dry was peppered with mounds of white powder. The water and detergent had formed a kind of slurry and when I was able to rinse it all out within a few days of the fish-box being dry it had mounds of white powder all over the flat bottom and a little up on the sides.

I too am aware that some aluminium boats have fish-boxes that are flooded with saltwater all the time the boat is stationary so I too am querulous as to why I have this issue with this one fish box. If it is something to do with the grade of aluminium it is a big issue because both fish-boxes are partly formed out of the deck panelling. Most of the deck is painted but even so the other side fish-box is not showing a problem. As far as I can see I cannot see corrosion in the bilge or anywhere else. I cannot see how anything is leaching into the fish-box from anywhere (unless something got in there inadvertantly and unknown to me while the boat was away).

As said earlier North River have commented on the photos that it is saltwater corrosion and that I could try to have it sandblasted but that I am only probably buying time until requiring to have the bottom cut out and replaced.

At this moment the fish box is sanded and looks good with no sign of corrosion apart from the obvious pitting. My next course of action is to apply muriatic acid and then paint with epoxy. Chaps has given me some advice as to how to apply. If the corrosion then returns I will have what is affected cut out and replaced. Unfortunately I do not have confidence in any local marine shop to assist and very much value the advice given by members of this forum.

I am sorry about the length of this post but I am trying to give all available information! I have also tried to post some photos but the files from my smartphone are too large. I will try again later.
BCTony
Posts: 103
Joined: Thu Feb 10, 2011 2:02 am
13

Re: Advice for Corrosion

#25

Post by BCTony »

Below are some photographs which might help.
The soap I used undiluted.
The soap I used undiluted.
The soap I used undiluted.
The soap I used undiluted.
The deck with large centre fish-box and two side fish-boxes
The deck with large centre fish-box and two side fish-boxes
Port side fish-box (with corrosion) after sanding.
Port side fish-box (with corrosion) after sanding.
Starboard side fish-box with no corrosion.
Starboard side fish-box with no corrosion.
Large centre-deck fish-box with no corrosion.
Large centre-deck fish-box with no corrosion.
Large centre-deck fish-box with no corrosion.
Large centre-deck fish-box with no corrosion.
Transom fish-box with no corrosion.
Transom fish-box with no corrosion.
Transom fish-box with no corrosion.
Transom fish-box with no corrosion.
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