Rust spots on stainless steel

[Astroscot2]

I noted while hanging around in the observatory a few days back that some of my stainless steel counterweights were starting to show a few small rust spots on them?

Can anyone recommend the best way to remove these without being too abrasive and also recommendation to stop them coming back.

Thanks

Mark

[Skipper Billy]

Are they Geoptik weights by any chance???

 

[Louis D]

Are they Chinese made perchance?  Chinese stainless steel is notorious for rusting in grills, kitchen knives, and other usages.  In comparison, I've had no problems with American or German stainless steel products rusting.

You can try using an aggressive brass or stainless steel cleaner and then sealing the surface with a clear urethane coating after you're done.  However, there's no guarantee it won't return.  I would just live with it knowing it has no affect on its usefulness.

[DaveL59]

Brasso may work, or believe it or not, tin foil scrunched up and rubbed against the area.

Can't comment re the above remarks about the steel makers but stainless does rust regardless of where it is made, usually tho if in contact with other metal like plain steel and in damp conditions. You can even find that on good quality stainless cutlery if left in the sink long enough with some other implement resting against it.

[wulfrun]

If it's ferritic stainless i.e. iron-containing, which is pretty certain if there's rust, put some phosphoric acid on it. You can buy phosphoric acid from aquatics suppliers (often called pH-down). Beware, it's seriously evil stuff so you'll need rubber gloves and eye-protection. Wash it off with water and dry carefully. It'll turn the rust into iron phosphate, passivating it but turning it black. As suggested, a lacquer of some sort afterwards would be good but the phosphated areas will not rust again.

[Astroscot2]

1 hour ago, Skipper Billy said:

Are they Geoptik weights by any chance???

 

Yes they are David, common problem?

[rrb24]

Mothers Polish is best.  I use it just like in this video:

https://smile.amazon.co.uk/gp/product/B0009H519Y/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

Edited November 27, 2020 by rrb24

[Craig a]

Yes depends on the grade of stainless, the best stainless would be 316 marine grade I’ve got 316 fittings on my boat and saltwater is highly corrosive but 316 has no rust.whereas my work trowels (I’m a plasterer) are stainless but lower grade and I get specks of rust on them all the time 

[newbie alert]

There's lots of grades of stainless steel,  only 316 is marine grade 

[Craig a]

1 hour ago, newbie alert said:

There's lots of grades of stainless steel,  only 316 is marine grade 

That’s my point if 316 can withstand sea water in my eyes that’s one of the best 

[Davey-T]

See if you can stick a magnet on it, that'll show if there's iron present.

As Dave mentioned rubbing with aluminium foil is good.

Dave

[wulfrun]

Unfortunately, most of the grades of stainless steel that actually live up to the name are difficult to work with, from a machining etc perspective. Grades like 304 and 316 would be nice to have but would you be willing to pay the price for something as simple as a weight?

[Skipper Billy]

23 hours ago, Astroscot2 said:

Yes they are David, common problem?

Yes - sadly it is.

As far as I know Geoptik don't claim that they are made from any grade of stainless steel let alone 316 grade.

They look very much like chrome plated mild steel and a very thin chrome plate at that.

I rubbed the rust away with a kitchen scourer using WD40 as a lubricant. Thoroughly degreased them and painted them with two coats of good quality varnish. Two years on they are still spotless.

All the best.

David (aka Skipper Billy)

 

PS - your name sound familiar - did I once lend you a power supply when you were having problems???  Some years ago !!!

 

 

[1parsec]

I'd buff it with a Scotchbrite pad and wipe over with an oiled cloth.  
Most stainless steel weights are made from 303 stainless steel which isn't 100% corrosion resistant.
316 has increased molybdenum which gives it the additional corrosion resistance.
Weights from 316 are possible but 316 costs more and takes longer to machine and would probably cost twice that of the same weight in 303.

[Oldfort]

I find that Autosol metal polish works well.  Easily obtainable from motor parts shops or on-line, and not expensive.  Plus you can buff up the chrome on your car or bike as well.

[steppenwolf]

On 27/11/2020 at 15:38, Astroscot2 said:

Yes they are David, common problem?

I have Geoptik weights on my Mesu 200 and they are not stainless steel but chrome plated as far as I can tell. I have kept mine completely corrosion-free by wiping then down from time to time with silicone-based lubricant which I apply liberally and only loosely wipe off.

[Seelive]

Search for passivating stainless steel, that should give you some possible solutions.

[m.tweedy]

I had the Geoptik ones as well. They are Chrome plated. I also used Autosol to clean them. It removed the rust but could not remove the pitting. The NEQ6 they were on has a new home now so i cannot say how they are now.

[Astroscot2]

21 hours ago, Skipper Billy said:

Yes - sadly it is.

As far as I know Geoptik don't claim that they are made from any grade of stainless steel let alone 316 grade.

They look very much like chrome plated mild steel and a very thin chrome plate at that.

I rubbed the rust away with a kitchen scourer using WD40 as a lubricant. Thoroughly degreased them and painted them with two coats of good quality varnish. Two years on they are still spotless.

All the best.

David (aka Skipper Billy)

 

PS - your name sound familiar - did I once lend you a power supply when you were having problems???  Some years ago !!!

 

 

Yes you did David,  I bought same power supply and have not have any issues. 

[Zermelo]

On 27/11/2020 at 15:23, wulfrun said:

If it's ferritic stainless i.e. iron-containing, which is pretty certain if there's rust, put some phosphoric acid on it. You can buy phosphoric acid from aquatics suppliers (often called pH-down). Beware, it's seriously evil stuff so you'll need rubber gloves and eye-protection. Wash it off with water and dry carefully. It'll turn the rust into iron phosphate, passivating it but turning it black. As suggested, a lacquer of some sort afterwards would be good but the phosphated areas will not rust again.

Also sold as Jenolite, the second-most-useful item in the impecunious motorist's toolkit, after WD40. 
It made up 75% of my first car, by the time I had to get rid of it.   

[wulfrun]

3 minutes ago, Zermelo said:

Also sold as Jenolite, the second-most-useful item in the impecunious motorist's toolkit, after WD40. 
It made up 75% of my first car, by the time I had to get rid of it.   

Yes I remember Jenolite, my Dad's favourite rust treatment in the days when cars' steel was biodegradeable. Jenolite only contains a few percent phosphoric acid though. Full-strength phosphoric is better for killing rust outright but needs to be handled with care.

WD40 is something I've always shunned, it's a water-dispersant (clue is in the initials, and the 40 is for "40th attempt") that seems to have gained a reputation is doesn't deserve as a do-it-all wonder fluid. It's pretty good as a water-dispersant and inferior for anything else. It also leaves a sticky film that attracts dirt if you don't clean it off after water-dispersing. I know this from the days when a car often needed help starting - due to cold, wet ignition leads. Ever tried GT-85? Half the price for twice as much of something that actually does do what most people think WD40 does - lubricate and prevent corrosion.

[JamesF]

8 minutes ago, wulfrun said:

Yes I remember Jenolite, my Dad's favourite rust treatment in the days when cars' steel was biodegradeable.

I've been there too :)

8 minutes ago, wulfrun said:

WD40 is something I've always shunned, it's a water-dispersant (clue is in the initials, and the 40 is for "40th attempt") that seems to have gained a reputation is doesn't deserve as a do-it-all wonder fluid. It's pretty good as a water-dispersant and inferior for anything else.

These days even the manufacturer says that it's good for almost anything.  They may have changed the composition of the product I guess, but I agree, there are better products for many of the purposes for which it often gets used.  Sometimes even just a splash of light oil.

James

[Zermelo]

39 minutes ago, wulfrun said:

Ever tried GT-85?

I'm afraid my earliest motoring days pre-dated its appearance.

41 minutes ago, wulfrun said:

Jenolite only contains a few percent phosphoric acid

Quite a bit, they claim. 
There are people on eBay and Amazon that sell the concentrated 85% stuff, but the postage is usually outrageous on small quantities - I'm assuming because it comes by special courier. Occasionally there is some that quotes regular postage rates; I ordered some once and it never arrived.

[wulfrun]

4 minutes ago, Zermelo said:

I'm afraid my earliest motoring days pre-dated its appearance.

Quite a bit, they claim. 
There are people on eBay and Amazon that sell the concentrated 85% stuff, but the postage is usually outrageous on small quantities - I'm assuming because it comes by special courier. Occasionally there is some that quotes regular postage rates; I ordered some once and it never arrived.

A good deal more than I recall. It's been a while since I saw a Jenolite container but my recollection was 3-5%. Seems I missed out a zero, I'll stand corrected.

[Davey-T]

1 hour ago, JamesF said:

I've been there too

These days even the manufacturer says that it's good for almost anything.  They may have changed the composition of the product I guess, but I agree, there are better products for many of the purposes for which it often gets used.  Sometimes even just a splash of light oil.

James

It's good for spraying on rusted on nuts and setting fire to it 😂

Dave