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Old 08-03-2013, 01:10 PM   #1
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Rusting stainless - thoughts or suggestions

Hello all, I'm looking for some feedback on rusting stainless steel. Being a former Great Lakes boater it is something I have never encountered before. I am well aware of the Taiwanese stainless issue and that the iron impurities will cause rust pitting particularly around welds but I'm finding even the "supposedly" North American stainless is rusting as well. The hundreds of stainless screws holding the rub rail on are the worst. Is there anything that can be done to control this? I have been wiping down or spraying every metal part on the boat with various anti-rust products but I can't tell yet if it is having any real effect at slowing or stopping it.

A few weeks ago I went to snug the huge stainless bolts on my rudder packing glands and was shocked when one simply twisted off with nearly no force. The stud looked brand new but the rust had nearly cut it in half just below the packing gland. All four studs were similar.

The second very strange rusting issue I am having is a very light overall rust discoloration or film on my railings and other things like my brand new barbeque.

The boat has an isolated AC ground and an extensive well cared for bonding system.

Being new to salt water I have no idea whats normal or not, any thoughts or suggestions?
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Old 08-03-2013, 01:19 PM   #2
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My bet...salt built up to point to make an anerobic and very salty water condition at the interface of the bronze packing and the stainless bolt. This would allow the stainless to rust and may have created a crevice crack corrosion situation that allowed premature metal failure.

Really not an expert here...hopefully someone will correct my simplification...

Fit's with the rule of thumb never use stainless where you can expect underwater or wet anaerobic conditions.
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Old 08-03-2013, 02:00 PM   #3
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Get some oxalic acid powder - mix it with dish washer soap - 1/2 quart to 200 grams powder (approximately) - thick enough that the mix can be applied with a paint brush and stay put. The rust amount determines how long to leave it there - probably a few hours.

Can also be used to rid the decks of bird Xhit and dirt. Works like a charm and dirt cheap.

Also removes rust stains from decks etc and it wont harm the FRP or topcoat (disclaimer - test for your self).
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Old 08-03-2013, 02:06 PM   #4
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I guess that I was a bit too quick there - I only know how to get rid of the stains - I don't know how to prevent rotten screws, so my guess would be to make an inspection or repair schedule for these items, to prevent them from becoming a problem.
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Old 08-03-2013, 02:26 PM   #5
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It certainly makes sense that it is due to salt build up from sea water leakage past the glands plus the issues of dissimilar metals. If this were the case however would not many of you have had the same problem? My old boats had bronze studs and bronze glands but my last few boats all had stainless studs so theoretically it should be a common problem today.

This also would not explain why all the screws in my rub rail are rusting (which are isolated from other metals) or the strange film rust discolouration I'm seeing on the rails & bbq.

I was half hoping someone would say this is common to all salt water boats but it is beginning to look like I have a real problem somewhere that needs to be addressed.
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Old 08-03-2013, 03:54 PM   #6
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Originally Posted by Capt Kangeroo View Post
Hello all, I'm looking for some feedback on rusting stainless steel. Being a former Great Lakes boater it is something I have never encountered before. I am well aware of the Taiwanese stainless issue and that the iron impurities will cause rust pitting particularly around welds but I'm finding even the "supposedly" North American stainless is rusting as well. The hundreds of stainless screws holding the rub rail on are the worst. Is there anything that can be done to control this? I have been wiping down or spraying every metal part on the boat with various anti-rust products but I can't tell yet if it is having any real effect at slowing or stopping it.

A few weeks ago I went to snug the huge stainless bolts on my rudder packing glands and was shocked when one simply twisted off with nearly no force. The stud looked brand new but the rust had nearly cut it in half just below the packing gland. All four studs were similar.

The second very strange rusting issue I am having is a very light overall rust discoloration or film on my railings and other things like my brand new barbeque.

The boat has an isolated AC ground and an extensive well cared for bonding system.

Being new to salt water I have no idea whats normal or not, any thoughts or suggestions?
Saying North American SS by it self doesn't' mean much. Most SS you buy is 304 which rusts more than 316 which is one the preferred marine SS. We've replaced 100s of screws, bolts, nuts and washer with 316 with good results.

Your grill is most likely 304. Dickerson and Magma are made from 304. Magma is pretty loose with their marketing brochure though, "Constructed entirely of 18-9 mirror-polished marine grade Stainless Steel" but it's still 304.

We had a bimini made and didn't specific the grade SS and got 304. It's a constant maintenance item.

SS fasteners are like hose clamps, not all are created equal.
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Old 08-03-2013, 04:13 PM   #7
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It certainly makes sense that it is due to salt build up from sea water leakage past the glands plus the issues of dissimilar metals. If this were the case however would not many of you have had the same problem? My old boats had bronze studs and bronze glands but my last few boats all had stainless studs so theoretically it should be a common problem today.

This also would not explain why all the screws in my rub rail are rusting (which are isolated from other metals) or the strange film rust discolouration I'm seeing on the rails & bbq.

I was half hoping someone would say this is common to all salt water boats but it is beginning to look like I have a real problem somewhere that needs to be addressed.
I did have the same problem...two nuts just crumbled off and I didn't feel my studs were in good enough shape to reuse....

I couldn't easily get replacement nuts or studs so I just drilled and taped my stuffing box to handle easily obtainable SS threaded rod and nuts from Home Depot.

I'll have to keep my eyes on it...but as a active cruiser I'm adjusting more than some others might.
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Old 08-03-2013, 05:24 PM   #8
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This is my favorite product for removing rust stains from stainless and fiberglass. The active ingredient is hydrofluoric acid. Spray it on and watch the stain disappear. You might have to rub a heavy stain.

You can get it in marine stores, hardware stores and grocery stores.

After you get it clean, Suncor Passivating Fluid might help prevent it from rusting again.
Link: Passivating Fluid
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Old 08-03-2013, 06:53 PM   #9
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Another option is plain white vinegar.
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Old 08-03-2013, 10:04 PM   #10
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Thanks guys, appreciate the feedback. From the sounds of things perhaps my situation isn't that unusual after all and it's simply a case of cheap stainless in a corrosive environment. I suppose I shouldn't be surprised, the tons of salt we spread on the roads in Canada can destroy even rust proofed cars in record time. I think I will follow Larry M's suggestion and start replacing my hardware with 316 if I can find it. The sad part of that however is I have built up a fabulous stock of stainless hardware and I bet none of it is 316.

Interestingly, my rubrail which is nothing more than a highly polished band of stainless doesn't rust at all, only the screws attaching it. Where the screws were imbedded in the wood they are "severely" rusted so perhaps this lends further support to PSNEELD's theory of concentrated salts.

The passivating fluid noted by HOPCAR may be the answer to prevention and I think I'll do some serious research on this.

Thanks guys
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Old 08-03-2013, 11:32 PM   #11
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Just finished spending some time on the site HOPCAR mentioned. There are some great articles on the site regarding this very topic. While I have not digested all of it yet, the big surprise was that "all" stainless rusts "regardless of where it was made" given the right conditions. The other interesting fact is apparently stainless needs oxygen to provide a protective oxide layer, this nicely explains why the embeded portion of my screws are rusted more severely than the rest of the screw. This also makes me wonder if I am not creating some of the problem by wiping all my stainless down with oil / wax based protectants. Much to learn yet!
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Old 08-04-2013, 12:14 AM   #12
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Yes - A big assortment of stainless steel types out there.
They all have different passivation potential so when you mix them, yous start running into trouble,
304 is fine in a fresh water environment, but add any chlorides and it will fail badly.
316 is the standard "marine" SS.
CK - It sounds like you have 316 rub rail and 304 screws.

Neither 304 or 316 can be used under water, but there a few types that can, if you can find/afford it. Super duplex and super austenitic stainless steels are suitable, and some prop shafts etc are made from this.

Monel is another material that works in sea water. BUT the differing materials can lead to big problems.

There was a boat built with a hull entirely of monel, which had to be scrapped after 6 weeks in the water because of the differing potential between the hull and the steel superstructure.
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Old 08-04-2013, 02:59 AM   #13
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Capt Kangaroo, I use SpotlessStainless, an amazing product.
You rinse the rust off, it's really incredible, even my signal horns, far away from SS, shine again. It's worth a try.
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Old 08-04-2013, 06:35 AM   #14
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There was a boat built with a hull entirely of monel, which had to be scrapped after 6 weeks in the water because of the differing potential between the hull and the steel superstructure.
What boat was that?
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Old 08-04-2013, 09:43 AM   #15
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I think I'd be thinking about replacing those hundereds of rail screws with good 318 screws b/4 they are too far gone and start breaking off when you try to remove them. I dont think you will ever stop the rust because it is at the interface (in the countersink) Most good fastener places, like Jamestown Dist, have what you need in 318. You may also have to clean or polish the countersinks as well. I would also apply sealant to the screws as you replace them to exclude water fron the countersink interface area.

Stainless has no place below the waterline anyway skeg bolts, rudder ports, stuffing box, and so on. All should be bronze fastened.
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Old 08-04-2013, 11:06 AM   #16
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A couple of things about SS.

The main protection is thin out coat much like chrome but.even thinner. Once that is cracked broken it will corrod.

SS has to breath O so not a good choise to embed cover.

SS comes in many grades kind so being SS does not mean much. All metal will corrod oxidize over time.
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Old 08-04-2013, 02:00 PM   #17
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A couple of things about SS.

The main protection is thin out coat much like chrome but.even thinner. Once that is cracked broken it will corrod.

SS has to breath O so not a good choise to embed cover.

SS comes in many grades kind so being SS does not mean much. All metal will corrod oxidize over time.

You may want to research that....as long as it has O2...it will not continue to corrode...

Stainless steel - Wikipedia, the free encyclopedia

Stainless steels contain sufficient chromium to form a passive film of chromium oxide, which prevents further surface corrosion and blocks corrosion from spreading into the metal's internal structure, and due to the similar size of the steel and oxide ions they bond very strongly and remain attached to the surface.[3]
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Old 08-04-2013, 02:42 PM   #18
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What boat was that?
Alexander Smith Cochran's schooner yacht Sea Call, built in 1915 in Neponset, Mass.

BIG YACHT NOW JUNK AFTER 6 WEEKS' USE - Sea Call's Monel Metal-Steel Hull Ruined by Electrolysis, Builders Admit. COSTLY EXPERIMENT FAILS Action of Sea Water Attributed by Metal Makers to Failure to Use Zinc Insulation. - View Article - NYTimes.com
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Old 08-04-2013, 03:37 PM   #19
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Responses from Australia, Austria, USA, Canada, the internet never ceases to amaze me. Thanks for the great links and advice guys.

I took a look at the product Spotless Stainless that DODO mentioned and although expensive I was quite impressed. They made one statement in their Faq section however that seems to be contradictory. QUOTE: If your stainless does not have enough Chromium to provide a protective oxide layer rust may appear quicker. In this case you may need to coat your Stainless after removing the rust and surface iron with Spotless Stainless Rust Remover.

This seems to suggest that if you have an inferior grade of stainless the key to controlling rust is to "prevent" oxygen from reaching it ie: the exact opposite treatment given to a higher grade stainless. Incidentally, this is what I have been doing but it is too early to tell if I'm helping or exacerbating the problem.

BROOKSIE, sounds like advice based on painful experience. As far as the rub rail and strakes are concerned, I am going to replace all the screws but I'm afraid it's great advice a little to late. A few have broke off already!

My next question will be how in hell to remove broken screws from fiberglass.
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Old 08-04-2013, 06:16 PM   #20
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I mounted new stainless cleats on a boat I was refurbishing and I used SS bolts, probably 304, and I used a lot of 4200 in the hole where the bolt went through as well as bedding the cleats.

A few years later and a new change and new paint. I remove the cleats and to my amazement the bolts were maybe 1/8th there in spots. It looked like wood that termites had eaten. I asked around and found out about oxygen deprivation of SS.

That's why silicon bronze is the preferred fasteners. They just don't work on stainless items.
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