On 08/10/2015 16:50, Chris Hogg wrote:
On Thu, 8 Oct 2015 16:12:54 +0100, Malcolm Race
wrote:

On 08/10/2015 15:08, Brian-Gaff wrote:
You might run a magnet over it.If it attracts, then its the kind that will
go rusty eventually as its an alloy with a ferrous metal of some kind.
Brian

All stainless steel contains a high proportion of iron i.e. it is a
ferrous metal. The different grades of stainless steel contain varying
proportions of chromium and nickel to make it corrosin resistant. For
instance yhe grade used for cutlery andgeneral houseware is known as
18/8. It resists corrosion in normal household applications but is not
suitable for use in contact with salt water

Malcolm

We had a dark room constructed at my former place of work, for
developing electron microscope plates. It had a standard
kitchen-quality stainless steel sink, probably obtained from a local
builders merchant. Within a few weeks it was heavily corroded and
rusty. They had to replace it with one made of a different grade of
SS. I couldn't tell you which grade, but it didn't corrode.

"Cheap" stainless is often slightly magnetic and not as corrosion
resistant as better grades such as 316. Dark-room chemicals are quite
corrosive and it does not suprise me that "cheap" stainless was not up
to the job.

Lightly rusted sinks/splashbacks etc will normally clean up OK with
scotchbrite and/or weak acids. It's the vinegar in tomato ketchup which
does the job.