Should 100% stainless steel never rust?

[Curiousgeorge]

Apologies for the seemingly obvious question but I was speaking to a guy who welds stainless steel for his employer last week and he said that he’s seen the steel rust before now. What does this mean? I was always under the impression that stainless steel meant it should never rust?

 

[Hitch]

Depends on so many things.

Grade of stainless, how its been treated, how its been fabricated, where its been used, what its come into contact with...

 

[Justme]

Its stain Less not stain never

 

[Curiousgeorge]

Very interesting. Sorry for the nativity - I always thought stainless steel should never rust and that’s why the food industry used them.

 

[eLuSiVeMiTe]

All steel rusts.
Ss has better resistance to it.

My kite buggies were 316 still had to clean the saltwater off to give it a chance. Used to find the odd rust spots. Or speckles would be a better description.

 

[pedrobedro]

Some stainless like 431 or 416 gets surface rust.

 

[Nick67GT]

Stainless steel is usually chosen for its corrosion resistant properties, but it is important to know that different grades provide different amounts of corrosion resistance. Austenitic stainless steels generally provide the most corrosion resistance because of their high amounts of chromium. This makes grade 304 an excellent choice when corrosion resistance is important. Grade 316 is similar to grade 304, but it has molybdenum as part of its chemical makeup, further increasing its corrosion resistance. Ferritic stainless steels and martensitic are generally more affordable than austenitic stainless steel because they have less nickel and sometimes less chromium than austenitic stainless steels, which can result in a loss of corrosion resistance.

Basically, as long as there is sufficient chromium present, the chromium oxide layer will continue to protect the stainless steel and prevent it from corroding.

 

[roofman]

Just be thankful that all things are not made with the same stainless as B&Q outside wall lights...those things only last for 3 rain days before going all weak at the knees

 

[brightspark]

Just be thankful that all things are not made with the same stainless as B&Q outside wall lights...those things only last for 3 rain days before going all weak at the knees

and are crap to fit made in china

 

[ronan]

If you allow stainless to rub against mild steel or grind mild steel and get the sparks on the stainless, it can also rust.

 

[Hitch]

Sharing abrasives between mild and stainless makes a difference too.

 

[eSCHEn]

Sharing abrasives between mild and stainless makes a difference too.

Always remember to practice safe grinding. Don't share discs!

 

[Rannsachair]

In my youth someone told me to test stainless with a magnet as the magnetic ones rust. I know now this is not always the case though it can for some of the common grades. As Nick67GT states, it really comes down to the higher Chrome and Moly content improves corrosion resistance.

 

[Shedendman]

Sharing abrasives between mild and stainless makes a difference too.

See,every days a school day,didnt know that

 

[roofman]

In my youth someone told me to test stainless with a magnet as the magnetic ones rust. I know now this is not always the case though it can for some of the common grades. As Nick67GT states, it really comes down to the higher Chrome and Moly content improves corrosion resistance.

This has baffled me when high end kitchen knives stick to a wall hung magnetic knife holder

 

[Shedendman]

Can i ask,whats with the numbers on SS ie 316 431 416 etc etc,why those numbers?

 

[Hitch]

See,every days a school day,didnt know that

Dont even share hand files between them at work.

Have a look here... 50 grades of stainlees.

 

[Rannsachair]

Can i ask,whats with the numbers on SS ie 316 431 416 etc etc,why those numbers?

You will get an overview on https://www.unifiedalloys.com/blog/stainless-grades-families/

 

[Curiousgeorge]

This was all brilliant!!!

 

[Kent]

Even cutting stainless on a guillotine used for mild steel csn contaminate the edge. Brushing a weld with a none stainless wire brush etc.
The best stainless work us done in separate work spaces with separate tools
Different crades for different purposes,, its only defined by the amount of chromium As stainless In the tool steel grades d2 is not a stainless being just under yhe mark but its non the less very corrosion resistent but 440 is, stainless and can rust just not as serve
Had to go on a course in Sheffield over 30years ago at thier stainless lab memory fades as i dont do much stainless at all now - sort of grew to hate tge stuff i feel