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Old 08-08-2016, 16:12   #1
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Rust stain

After a few days offshore, our friends boat started showing signs of rust staining on the topsides and along the sides.

[ATTACH]129163[/ATTACH

A few observations,

The bow nav light seal around lens is cracked, allowing seawater into the fixture. The inside shows lots of internal corrosion.

Other cruisers infer the SSB introduced a grounding issue and could cause stray current.

One of the cabin light circuits has a large voltage drop and seawater made it into one fixture.

All the lifelines and chainplates are electricly tied together - I don't think they are connected to the battery ground.

Clearly there's electrically induced corrosion occurring around the stanchions.

Any thoughts on the cause of rust?
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Old 08-08-2016, 16:18   #2
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Re: Rust stain

That's not a few days. Appears to be a few years sitting in a marina to me.
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Old 08-08-2016, 16:19   #3
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Re: Rust stain

Surely those rust stain in the pics can't be from only a few days.
This is clearly a sign of poor bedding and water retention.
Remove, re bed, clean stainless with a good pickling jelly like "spotless stainless"
Problem solved.
Have to wonder what's going on under all that like water intrusion into the core or hull to deck joint
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Old 08-08-2016, 16:26   #4
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Re: Rust stain

The picture is after 14 days from San Francisco to Hawaii. We noticed the stain after a couple days and it got progressively worse during the passage.

Certainly need to rebed all the deck hardware.

Any way the SSB could have caused this?

I'm worried about electrically induce galvanic corrosion - from bow light fixture, cabin light or SSB.


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Old 08-08-2016, 16:33   #5
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Re: Rust stain

Seems severe for galvanic activity above the water line.
Get a zinc any zinc attach to one lead of muti meter and put in the water,
Put other end on rusting stainless (make sure you have a good connection)
Anything over .3 volts is problematic. I'd suspect if this is due to electrolysis you would have 2-3 volts not good!
I'm sure there are many more qualified members out there that will comment.
But if this happened in a few weeks you've got a serious problem.

Love to here update
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Old 08-08-2016, 16:42   #6
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Re: Rust stain

Somebody re-mounted/rebedded things using crap fasteners is my bet. Where else besides the stanchions are you seeing severe rust bleeds like that? As if the stains are only near say, deck hardware, & things like the stanchion bases themselves are of quality, then it's a fasteners issue.

Not to be harsh, but I'd give you 50:1 odds that the stanchions aren't part of the SSB's ground plane. And if they only started corroding at sea, then what I'm saying jibes. As they wouldn't much get wet via salt water at the dock or on a mooring, where as on an offshore passage...


Edit: I'm assuming that the boat's fiberglass? And what type of boat, & year? As it's also possible that the factory used poor quality fasteners when she was built, if they're the culprit.
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Old 08-08-2016, 16:56   #7
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Re: Rust stain

Thats pretty active, use Nitric acid, 30% to passivate, then multimeter to investigate.
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Old 08-08-2016, 17:26   #8
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Re: Rust stain

I'm going to guess/suggest that the culprit is a galvanized fastener (or 2 or 3 ...) in the rubrail. Note the rubrail joint where the stain emanates from.
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Old 08-08-2016, 19:40   #9
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Re: Rust stain

SSB ground was Kiss SSB, not connected to any boat's ground. Completely independent.

Possibly cheap fasteners at stanchion base or rub rail.

I can't check voltages till boat gets home.


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Old 13-08-2016, 16:22   #10
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Re: Rust stain

Now that I'm finally home, I reread everyone's posts and thought about this more. Attached are a few more pictures to further this discussion. To summarize what's probably going on, along with my opinion,

The boat is a 18 year-old Tartan. In my opinion, the boat is well maintained and was ready for the passage to Hawaii. All of the critical systems were replaced or upgraded, though as we discovered, a few things lead to problems along the way.

The rust is mostly concentrated around the stanchion bases and the rub-rail. Photo "race start" shows a clean deck (yes that's a whale outside SF Bay). Photo "14 days later" shows the stained deck (with an small experiment cleaning the deck using Barkeepers Friend on stbd by cockpit).

It is interesting that the "bow" picture shows staining on the bow pulpit by the nav-light. As seen in photo "bow-light" the nav-light also shows serious corrosion at the base and further on the inside of the fixture. The bow-light stopped working a couple days into the trip. The nav-lights were on at night for stern light.

There were also signs of corrosion inside the stbd cabin light in the v-berth. During the trip, I did notice that the stbd run of cabin lights were not working properly. The LEDs were flickering and sometimes wouldn't light. After the race, I measured the voltages and saw 8 volts at the forward electrical connection and along the starboard side. I also noticed a few bad electrical splices along the run.

I agree with Panacea, it sure looks like accumulated build-up of rust, poor bedding and possibly poor quality screws at the stanchions and the rub-rail. Chainplates and the standing rigging are clean -- probably due to better quality stainless.

The fact that the bow-light stopped working early in the trip and was awash in sea-water throughout, implies to me that with each wave breaking over the bow, 12 volts was emitted into the salt-water and created a stray current. Per "bow-light" photo, the 12 volt plus and minus contacts were exposed to salt-water and they corroded. This appears to be caused by a broken plastic gasket between the base and lens. Also, the bottom screw holding the lens to the base was stripped. The fixture was not sealed, wet, exposed to sea-water and energized for 8-10 hours per day. I believe this introduced current into the boat and accelerated the corrosion on the lower quality stanchion screws.

Likewise, there is a 4 - 6 volt drop along the interior stbd cabin lights electrical wiring. The v-berth portlight appears to be leaking, letting salt-water into the light fixture, photo "wet-cabin-light". My original thought was this introduced stray current into the boat and to the nearby common grounding wire connecting the stanchions. This clearly is a problem, but after discovering the bow-light, I don't believe the interior cabin lights are not the major cause.

It is possible that this is not related to any stray electrical current throughout the boat. Instead, this might be completely due to poor quality screws and bedding. Over the years, the screws may have been corroding away and the rust may have accumulated at their bases and deck core. Only when washed out by constant breaking waves over the sides, did the build-up leach out and stain the deck/sides.

A lot of folks at the yacht-club thought the problem was due to the SSB installation. Their claim is the ICOM 802 installation manual describes grounding the radio and tuner to the stainless steel stanchions, etc. using copper foil (I verified this on page 55 ic-m802.pdf installation manual). I don't have an ICOM 802 (on my wish-list); I have an old SEA 235 radio. My installation manual describes connecting the antenna tuner to a suitable "RF ground" and no reference to grounding the radio to the RF ground. In discussing this with SEA radio technical support, "the ground stud on the radio is duplication of your DC minus battery connection, should be connected to a close ground if the DC minus lead is very long. The critical connection for the RF ground is the stud on the antenna tuner...". I didn't see a lot of RFI issues on this boat.

The SSB was used for at most an hour per day and was not connected to the common grounding wire between the bow pulpit, stanchions and stern pulpit. I can't imagine any stray current between the radio 12 volt ground and ships ground or RFI creating such a severe case of corrosion. Furthermore, I've used the same radio, antenna and Kiss-SSB ground on 2 different boats (similar offshore conditions) and never seen this problem. I don't believe the SSB had anything to do with this.

I plan on measuring the voltage between the stanchions and seawater - I will do this once the boat is home. I also am going to try to simulate waves breaking over the bow-light, to see if that changes the voltage reading. That would confirm my belief that the bow-light introduced current to the stanchions. Good thing this is only 12 volts!

Aside from the electrical issues with the bow-light and cabin lights, I'm now concerned about poor bedding and accumulated corrosion at each of the stanchion bases. Years of accumulated water build-up might lead to damaged deck core material that requires more extensive repairs. We didn't have a chance to remove a few of the stanchion screws to see the extent of the problem. Once the boat is home, we'll certainly remove them all, check for core damage, rebed and replace the hardware.

I welcome further discussion on this, though we won't have the boat back for a few weeks.

Thanks!
Don
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Old 13-08-2016, 18:41   #11
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Re: Rust stain

Ignoring the lights with water in them, is it possible someone used steel [not stainless] wool to shine up the stanchions before departing on this trip? That could also account for the rapid appearance of localized rust...

Just thinking out loud...

Best wishes resolving this issue.

Cheers! Bill
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Old 13-08-2016, 18:50   #12
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Re: Rust stain

Quote:
Originally Posted by wrwakefield View Post
Ignoring the lights with water in them, is it possible someone used steel [not stainless] wool to shine up the stanchions before departing on this trip? That could also account for the rapid appearance of localized rust...

Just thinking out loud...

Best wishes resolving this issue.

Cheers! Bill
Bill - many years ago, I stupidly used steel wool when varnishing another friend's boat's toerail. That was a very impressionable mistake, spending weeks cleaning millions of rusted steel wool bits from his gelcoat. The interesting thing is these steel wool bits left tiny semi-circular rust patterns about 1/8" long, deep in the gelcoat. In this case, I didn't see any indication of rusting bits in the gelcoat.

I appreciate thinking outside the box - I don't think this is the case
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Old 13-08-2016, 19:53   #13
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Re: Rust stain

Quote:
Originally Posted by Capt.Don View Post
Bill - many years ago, I stupidly used steel wool when varnishing another friend's boat's toerail. That was a very impressionable mistake, spending weeks cleaning millions of rusted steel wool bits from his gelcoat. The interesting thing is these steel wool bits left tiny semi-circular rust patterns about 1/8" long, deep in the gelcoat. In this case, I didn't see any indication of rusting bits in the gelcoat.

I appreciate thinking outside the box - I don't think this is the case
Hi Don,

Good point about the tell tale signs of steel wool... None of us are immune to that lesson, or the one about being near a steel boat with someone grinding on it- sometimes even rotary wire brushes...

I have had great success cleaning fiberglass stains- including rust- using phosphoric acid. [e.g., Ospho] I don't know what else works.

What have you had success with for cleaning rust stains?

Cheers! Bill
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Old 13-08-2016, 21:02   #14
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Re: Rust stain

Oxalic acid - found in Barkeepers Friend and wood bleach.

Also forgot to mention - millions of pin-point rust dots too.
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Old 14-08-2016, 08:41   #15
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Re: Rust stain

Oxalic acid should take care of the stain. It's available at Marine stores in crystal form. Also the active ingredient in 'Barkeeper's Friend' if you want to polish up the SS while you are at it. Make up a solution if you buy the crystals, brush on, wait a few minutes and rust will magically disappear.

As far as cause, would bet someone used a ferrous containing scrubbing agent to clean the stantions, SS rails, etc. Looks like all the SS hardware on deck was affected. Did the owner higher some clown off the street to detail the boat before the cruise.

Suggest the owner pull all the on deck hardware and rebed using a good marine sealant, not silicone. Leaks through the deck will soon cause mushy core rot if the core is Balsa or Plywood.
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