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Cleaning rust from stainless
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AstoriaDave



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PostPosted: Sun May 03, 2015 3:19 pm    Post subject: Reply with quote

I'll try. The chromium in the alloy in the form of its oxide forms a protective coating on the underlying alloy. If the stainless is held in an oxygen free environment (aka "anoxic"), it is possible for the chromium oxide to be degraded, exposing the underlying alloy, and allowing it to be eroded away. The technical term I know for this is "crevice corrosion".

That said, my local shipwright claims stainless burried within a wooden structure and not exposed to water will last forever.

One source which explains the corrosion in more formal terms: http://www.corrosionist.com/Pitting_Crevice_Corrosion.htm

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journey on



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PostPosted: Sun May 03, 2015 3:32 pm    Post subject: Reply with quote

Quote:
"Stainless steel is not resistant to chemical or physical attack. The corrosion resistance of stainless steel depends on the formation of a 'passive surface film' composed of nickel and chromium oxides (Cr203 & Ni0). Passivation involves removing free Fe or 'tramp Fe' from the stainless steel surface."
End quote

Boris
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hardee



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PostPosted: Sun May 03, 2015 7:44 pm    Post subject: Reply with quote

smckean (Tosca) wrote:
Quote:
Both need oxygen to delay rust incursion and corrosion

Harvey, I am confused by this. Can you explain it to me? Thanks


Dave and Boris are much better at it than I am for the technical side. Practically, if you put tape on a stainless tube, it will corrode or rust under the tape faster than on the rest of the surface.

Harvey
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gulfcoast john



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PostPosted: Tue May 05, 2015 6:55 pm    Post subject: Reply with quote

Hi Brats!
Sure, Oxalic acid in all its various forms will remove rust tarnish from SS, but also your Poli-Glow clear coat (outlier alert!) or wax if you like wax, and it will stain your aluminum trailer (wet it down first) and it's not good for your skin or eyes.
For years I've been using Woody Wax...a cheap Lowes type cotton glove over a vinyl glove (optional, but it keeps the harmless stuff off your hands), spray the outer cotton glove with Woody Wax. Use some bronze wool in stained areas and just The Glove on nonstained SS rails and bimini supports. The cotton glove allows you to get the liquid around post bases etc without hitting your Poli-Glow and is very, very fast and easy and benign. Leave it on as little as 1 hour or 24 hours for tough stains, then wipe it down with a terry rag (or microfiber cloth) and you will have a shiny protected SS rail for up to 3 months in the Deep South. Stash the Cheap Cotton Glove and the used bronze wool in a zip-lock bag for future use (if you're as cheap as I am). Don't even try to use SS or steel wool. The bronze wool can be re-used many times. I bought a gallon of Woody Wax (half price) at the last day of the 2011 Miami Boat Show we are still using. It's also great to get the wax off the plastic black nav light housings and shine up any plastic/composite plastic, as well as a non-skid cleaner and non-slick wax/protectant for your non-skid areas. Also, it tastes great sprayed on Rocky Road Ice Cream (JUST KIDDING!). I've also liked Miracle Cloth but you can't let it contact water and overall Woody Wax is cheaper.
Here are the West Marine prices, but you may well find better searching elsewhere.
http://www.westmarine.com/buy/western-pacific-trading--bronze-wool-pads-fine--P004_126_004_510
http://www.westmarine.com/buy/woody-wax--fiberglass-non-skid-deck-wax-woody-wax-16-oz--3745320
Cheers!
John

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hardee



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PostPosted: Thu May 07, 2015 12:33 am    Post subject: Reply with quote

I spent some time with a metal fab shop today. The owner said I need to look into "passivating"

So I found it is a chemical process and not something I can brush on and mask around. Anyone have any practical experience with that?

Harvey
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Will-C



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PostPosted: Thu May 07, 2015 8:30 am    Post subject: Cleaning rust from Stainless Reply with quote

Prism Polish
Prism Polish
Metal Polish and Fiberglass Deoxidizer


Prism Polish has been formulated to clean, polish and protect all metals in one easy application. Our protective coating is designed to last 3 to 6 months. Prism Polish contains no harsh acids, caustics or abrasives. it is safe to use on all metals fiberglass, gel-coat, plexiglass and painted surfaces. Prism Polish has been developed for use in the marine, aviation, automotive, motorcycle and maintenance industries. Use Prism Polish on bronze, brass, copper, stainless steel, aluminum, pewter, nickel, sterling silver, silver plate and factory blued guns.It offers the finest protection available for any chrome or stainless surface. It cleans and protects in one easy application. It restores tarnished and dull surfaces and protects against salt corrosion and rusting. Prism Polish is excellent to clean and deoxidize fiberglass, It removes cloudiness from plexiglass, clear vinyl, eisenglass or Lexan. www.prismpolish.com you can purchase on Amazon

This stuff seems popular with the Tugnuts. It's what we have been using for years.

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AstoriaDave



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PostPosted: Thu May 07, 2015 11:34 am    Post subject: Reply with quote

hardee wrote:
I spent some time with a metal fab shop today. The owner said I need to look into "passivating"

So I found it is a chemical process and not something I can brush on and mask around. Anyone have any practical experience with that? ]
Harvey, no hands on experience here. However, a skim of this article may illustrate why passivation is never going to be a realistic answer for corrosion protection of railing or other stainless hardware installed on the boat. I think it is really only useful for original parts fresh from machining, with rigorous monitoring of the passivating materials and conditions. Too bad. BTW, I have never seen SS treated for passivation with a shiny, mirror finish. Always matte, always sort of gray. I suspect this is due to the need to avoid contamination of the surface.

http://www.mmsonline.com/articles/how-to-passivate-stainless-steel-parts
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thataway



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PostPosted: Thu May 07, 2015 1:02 pm    Post subject: Reply with quote

I have had SS exhaust fittings fabricated for several boats. These were always passivated. As Dave describes, the surface is dull, and has a gray color.
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Sea Wolf



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PostPosted: Thu May 07, 2015 1:42 pm    Post subject: Reply with quote

OK, here's what I know:

Stainless steel is Iron + carbon, iron for the matrix/strength, carbon for more strength and hardness.

Nickel, chromium, and (sometimes like in 316) molybdenum, are added, all for anti-corrosive properties, as well as some other properties they give the alloy.

The oxides of Ni, Cr, and Mo are what actually protect the steel. The surface of stainless must consist of these oxides. These three metals readily form the oxides when exposed to air.

Any iron atoms on the surface can rust (form iron oxide or rust) with oxygen and water in the air.

When hardware is made with stainless, the various forming process of cutting, machining, welding, etc., leave loose carbon atoms on the surface.

Passivation consists of removing these iron atoms on the surface by various means, such as chemically removing them, eg., "pickling" them with citric acid, though several other processes exist, such as electro-polishing.

Some of the chemical processes etch the surface, leaving a dull, matte finish, unlike elecro-polishing.

Some polishing compounds you can buy claim to "re-passivate" stainless, although I doubt they match the industrial processes.

Waxing the stainless helps protect it for a limited time.

One thing I do know is that if you use regular steel wool, a steel brush, or a file or a similar tool on a stainless piece and then re-use the hardware piece, the contact with the regular steel will leave untold billions of iron atoms on the surface (microscopic welds are made between the regular steel and the stainless, then broken), and the hardware piece will then rust like crazy. A stainless wire brush/wheel is much better, but without re-passivation of the surface afterward, rust still shows up fairly quickly .

I learned this from a metallurgist/welding fabrication supervisor in our sailing club that worked at the Marine Division of Westinghouse in Sunnyvale, California.

Sorry about the retired science teacher blackboard drill, but still can't shake the habit! Laughing

Hope this helps!

Joe. Teeth Thumbs Up

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Aurelia



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PostPosted: Thu May 07, 2015 1:52 pm    Post subject: Reply with quote

We love flitz polish and it does double duty and a wonderful and safe cleaner for plastics and fiberglass. Pack one bottle and you can clean/polish nearly anything on the boat. The bottle form is good but more watered down. The paste form in a tube is best. Goes a long ways too.....

http://www.midwayusa.com/product/752367/flitz-paste-metal-polish?cm_mmc=pf_ci_google-_-pf_ci_google-_-pf_ci_google-_-pf_ci_google&gclid=CLXek4SZsMUCFUeUfgodZDMAuQ

Greg

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AstoriaDave



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PostPosted: Thu May 07, 2015 4:13 pm    Post subject: Reply with quote

Joe,

Thats a good summary. The link I posted has more detail for those interested.

Oh, one typo. Your first line describes ordinary steel, aka carbon steel. Not stainless until those other guys get into the act. Then comes the black magic.

That business about steel wool screwing up stainless is worth remembering. I also wonder how someone could repassivate a surface after machining or sanding it. I don't see over the counter polishes as capable of doing that.
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Sea Wolf



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PostPosted: Thu May 07, 2015 7:27 pm    Post subject: Reply with quote

AstoriaDave wrote:
Joe,

Thats a good summary. The link I posted has more detail for those interested.

Oh, one typo. Your first line describes ordinary steel, aka carbon steel. Not stainless until those other guys get into the act. Then comes the black magic.

That business about steel wool screwing up stainless is worth remembering. I also wonder how someone could repassivate a surface after machining or sanding it. I don't see over the counter polishes as capable of doing that.


Dave- That's what I meant:

Iron plus carbon = steel,

then with the other elements it becomes stainless.

Thanks for the positive comments!

Joe. Teeth Thumbs Up
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AstoriaDave



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PostPosted: Thu May 07, 2015 9:41 pm    Post subject: Reply with quote

Joe, Big DOH here. guess I did not process that very well. Laughing
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hardee



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PostPosted: Fri May 08, 2015 2:04 am    Post subject: Reply with quote

Joe,

No need to apologize for your methods. They worked for years, so must be perfected, and still works here -- at least for me. Thanks for the explanation.

Lesson being learned: It's good to go with the pro's.

Harvey
SleepyC Moon

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SEA3PO



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PostPosted: Fri May 08, 2015 11:37 am    Post subject: Reply with quote

I agree about how to polish the stains out of stainless.. I use Bartenders Friend... acid works really easy too.

some stainless hardly shines at all...

It is the Chrome content that really sets the properties of Stainless Steel...a low grade (soft) stainless can have as low as 2% Chrome content, while a very hard, highly bright (ease to polish),very corrosion resistant stainless will have up to 17% Chrome content.

Joel
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