Leaking Leedal darkroom graduated Measuring container

[David Lobato]

A pin hole in stainless steel may be from a manufacturing defect. Does Leedal have a lifetime warranty? You could contact the company and request a replacement.

[Duolab123]

How did that happen?

Intergranular corrosion, some one must have carelessly left it in a wet spot in contact with Iron, steel. I would use JB weld or it could be welded and polished out by somebody who knows what they are doing. Heck of a note. 3M makes stainless steel tape, it's price is astronomical.
Mike

[Duolab123]

Many stainless steels are susceptible to pitting corrosion (type 316 is specifically formulated to be resistant) which can be caused by any bit of more active metal (usually, iron) contacting it in a wet environment. The chemistry is a bit complicated, but the basic idea is that once the (normally protective) surface oxide is breached, the electrochemical cell propagates corrosion underneath the contamination. Eventually, this can create a pinhole as you describe.

If you are lucky, this was caused by the graduate sitting on something like a steel nail in wet wood for a long time. If you have bits of iron stuck to the bottom of the graduate, though, the problem will most likely eventually return. (There is a reason why the instructions for most stainless steel ware tell you not to clean with steel wool; you can and should either use an abrasive cleanser or buy stainless steel wool.)

Chloride ion (as in salt water) is rather aggressive towards stainless steel in the absence of oxygen; an interesting corrosion demonstration involves a rubber band stretched around a piece of Type 304 stainless and then placed in a bottle of salt water. The steel will corrode under the rubber band (where oxygen is excluded) forming notches which will eventually cut the steel in half!

I worked for major manufacturers of Home appliances for over 20 years, I remember when we first had to start making SS refrigerators and other articles. SS even 300 series is a pain in the butt for appliances. Now most companies use even cheaper 430 grade, a lot of which are clear coated for "fingerprint resistance" which also dramatically improves corrosion resistance. As you say once the chromium oxide is disturbed SS is vulnerable. Nikor in the good old days recommended passivation with dilute nitric acid for tanks. Stainless steel is a fickle, no iron and no chlorine.
Mike

[Harold_4074]

Epoxy 2 part mix, outside surface of the graduate

Close, but not quite---fill the hole from the inside, and make sure that there are no crevices either inside or outside; since the pit may be wider below the surface than you can see from the outside, it wouldn't be a bad idea to carefully drill it out until all corrosion is gone, and then patch.

Wikipedia has a fairly readable articles on "crevice corrosion" and "pitting corrosion" that you might want to check.

In general, it is good practice to wash and dry stainless labware after use; my developing tanks all came with Leedal stickers saying "Keep it clean to keep it stainless".