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skipgundlach · 15-07-2018, 12:12

Be cautious with any form of oxalic acid to rinse it off very thoroughly, and, better yet, follow on with Collinite Metal Wax, and then Insulator Wax (850 and 845 respectively).

Later cleaning of spot rust is a breeze with Metal Wax, and a nice protective layer goes on with the insulator wax. Both essentially wipe on, wipe off, though you may have to buff if you get more than a little surface rust, and depending on the grade of SS.

There is a jelly product the name of which I forget which is better than spotless stainless, which is really designed only to take off surface rust, which it does admirably, but also must be rinsed thoroughly.

model 10 · 15-07-2018, 12:20

The Nitric acid that is used for concrete etching does come in a gallon bottle but is is only 20% nitric and 10% Phosphoric and water, I think.

skipgundlach · 15-07-2018, 12:50

Quote:

Originally Posted by skipgundlach

Be cautious with any form of oxalic acid to rinse it off very thoroughly, (clip).

Sorry - I forgot to say why.

If you don't rinse thoroughly, it will actually enhance further/later staining...

hellosailor · 15-07-2018, 14:00

Oh yes, I'm familiar with nitric acid and stainless steel. Don't ask me how long ago or why.

I don't think I'd want to play with it on a boat. In fact, I KNOW I don't want to play with it on a boat.

skip-
No, I haven't tried using citric directly. I've no idea where to get that any more concentrated than lemon juice these days, and no great interest in setting up a big dipping tank to really test different acids, or make up different mixes, hoping that colloidal additives won't affect the acid action, etc.
Someone else will have to do the lab project.(G)

**hpeer** · 15-07-2018, 14:50

I don’t know if it works but Rustoleium makes a gooy type rust remover that can be spray or whiped on. It’s some kind of acid with a thickener.

Ramona · 15-07-2018, 15:56

For Australians I would recommend "Metal Gleam". I have used it for 30 years or so. Excellent on fibreglass and works well on paint work prior to re coating. Widely used in the fishing industry.
https://www.nowchem.com.au/wp-conten...etal-Gleam.pdf

jacktheflyer · 15-07-2018, 16:47

Quote:

Originally Posted by Ramona

For Australians I would recommend "Metal Gleam". I have used it for 30 years or so. Excellent on fibreglass and works well on paint work prior to re coating. Widely used in the fishing industry.
https://www.nowchem.com.au/wp-conten...etal-Gleam.pdf

This is largely Phosphoric Acid (rust converter) with a Nonylphenylexoxylate in a smaller quantity I imagine as a surficant to promote coverage of the acid.

All the responses I've seen here and other forums seem to recommend products with the following main active ingredient in order of least hazard/effectiveness:

Citric Acid
Phosphoric acid
Oxialic acid
Hydrochloric acid
Nitric acid.

All are effective though the first three are considered to be benign enough for us amateurs.

I did see on this post a recommendation for Hydroflouric Acid. This is an extremely hazardous chemical which will etch glass. The only place I have seen it domestically is as a trace chemical in Aluminium Brightener. It is often confused with Phosphoric acid.

However the original question was how to passivate the stainless. Stainless is steel that is passivated by the addition of nickel and chromium. I don't know how you can improve on this other than to paint it or wax it. However if I use a metal polish on my SS it does seem to resist staining longer.

Scrubby

Ted and Relinda · 15-07-2018, 20:35

Bar Keepers Friend.....works great. Buy as a dry cleanser type like Ajax or liquid like soft scrub. You'll find it right next to named item in the grocery store. Works great on our stainless ... Ted.

HopCar · 15-07-2018, 21:23

[QUOTE=jacktheflyer
I did see on this post a recommendation for Hydroflouric Acid. This is an extremely hazardous chemical which will etch glass. The only place I have seen it domestically is as a trace chemical in Aluminium Brightener. It is often confused with Phosphoric.

Scrubby[/QUOTE]

The product I recommended for rust stain removal is made by Rustoleum and is called Whink. I imagine it is a pretty dilute solution but it is hydroflouric acid.

There are some pretty scary warnings on the label. They do warn that it will etch glass but it doesn’t happen fast. They also say it’s not for use on stainless. I imagine it would dull highly polished stainless but if the stainless is rust stained, it’s not highly polished any more. I also keep a hose handy to rinse it off.

It works great for removing rust stains from fiberglass.

It is available in the US in just about every grocery store and hardware store, as well as Walmart, Target and Amazon.

I’ve been using it for more than forty years without a problem.
https://www.walmart.com/ip/Whink-Rus...FL-OZ/15716648

IMACSS · 15-07-2018, 21:28

Polishing Stainless Steel (SS) is dear to my heart as I have had a few attempts but not sure of the value of my input here. Here goes as I have taken notes of the great suggestions on this thread so far:

(1) Firstly (CAUTION) - I use a product called Avesta Pickling paste after welding SS which I understand has some passivation properties. It comes as a blue/green/red/clear gel that can be painted on as well as a spray.

Please note that this product should be used with caution as it contains Sulphuric, Nitric and Hydrofluoric acids which have some terrible outcomes through contact with skin, eyes, mouth and inhalation etc. It is also not environmentally friendly BUT is water soluble at least.

Pros - It works and it needs very little quantity etc
Cons - Please read notes above, I would not like to store it on my boat and PPE is definitely required. Possible expensive as well.

(2) After using the pickling paste and as a cleaning agent I use a metal polish called Autosol. LINK to the MSDS/SDS http://autosol.com.au/wp-content/uploads/2014/07/msds_autosol_1000.pdf (copy and paste ??)

Autosol is found in most auto shops etc and is non-hazardous and not a dangerous goods and comes as both a liquid and a fine paste. It is easy to apply and remove and appears to apply a thin film to protect the surface (for a while at least)

Pros - It works, easy to apply and I do have some on my boat
Cons - A little expensive and needs to be reapplied occasionally

Thanks heaps for the discussion and hope I've added some value.

Toys_with_time · 15-07-2018, 22:59

Quote:

Originally Posted by a64pilot

Citric acid does work, and does work well.
You should avoid nitric acid, it’s pretty dangerous stuff, and how do you dispose of it?

Passivation is not a brush on and walk away thing unfortunately , there is a process that must be followed to achieve best results, like anything.
I know you won’t believe me, and of course I can link to a study that is trying to sell you citric acid, there are a lot of those, but perhaps you’ll believe these guys.
https://ntrs.nasa.gov/archive/nasa/c...0110001362.pdf

Interesting article but to me the critical result from a sailing perspective is that they say that without heat citric acid doesn’t passivate

TwT

**Wotname** · 15-07-2018, 23:00

Quote:

Originally Posted by HopCar

The product I recommended for rust stain removal is made by Rustoleum and is called Whink. I imagine it is a pretty dilute solution but it is hydroflouric acid.

There are some pretty scary warnings on the label. They do warn that it will etch glass but it doesn’t happen fast. They also say it’s not for use on stainless. I imagine it would dull highly polished stainless but if the stainless is rust stained, it’s not highly polished any more. I also keep a hose handy to rinse it off.

It works great for removing rust stains from fiberglass.

It is available in the US in just about every grocery store and hardware store, as well as Walmart, Target and Amazon.

I’ve been using it for more than forty years without a problem.
https://www.walmart.com/ip/Whink-Rus...FL-OZ/15716648

Yes, I'm sure it is very very dilute solution.
Hydroflouric acid is a dangerous acid for the unwary and in Australia a permit is required to buy or store for any solution of 1% (or greater). Permits are not given lightly or for non commercial uses. A sober account of a HF death is here http://www.ehs.ucsb.edu/files/docs/ls/HF_fatality.pdf

And for general guidelines see
https://www.commerce.wa.gov.au/sites...uoric_acid.pdf

**Wotname** · 15-07-2018, 23:07

I'm surprised of the several post that references nitric acid for concrete etching / cleaning.

All the concrete etching products that I have seen or used are muriatic acid (AKA hydrochloric acid), not nitric acid. A quick search google suggests the same - but I'm happy to be loved wrong.

stnick · 16-07-2018, 07:46

i vote spotless stainless
Brush on wash off once a year !

model 10 · 16-07-2018, 08:21

Quote:

Originally Posted by Wotname

I'm surprised of the several post that references nitric acid for concrete etching / cleaning.

All the concrete etching products that I have seen or used are muriatic acid (AKA hydrochloric acid), not nitric acid. A quick search google suggests the same - but I'm happy to be loved wrong.

Sika Concrete Etch. It's ok to love being wrong.