any idea what kind of metal this is

[Yggdrasil]

Additionally, stainless are not corrosion free unless it is clean.
Even a speck of paint or other pollutants may/will start a reaction of corroding.
We worked with stainless equipment for the food industry for years.
Often when we came back to service the equipment it was a sad sight.
Needed to retreat it with "whink/ or similar" and polish it up again.

But water had no effect.

We worked exclusively with the 300 series for this.

 

[kurtak]

Additionally, stainless are not corrosion free unless it is clean.

This is correct

There is why it is called stainless & not stainproof

In other words - it stains (corrodes) less then normal iron or steel --- but that does not make it stain (corrosion) proof

Kurt

 

[4metals]

I used a 1/2 inch diameter clear PVC tube That I filled with Water, then I covered one end with my thumb and then the free end with the water in it was put under the surface of the Nitric in the SS container then I moved my thumb off the outside end , then the acid Siphoned out of the SS into a glass container.

Is there any chance you used the same procedure and the same siphon to siphon acid from your hydrochloric tank? If so was it possible that a small amount of Hydrochloric Acid remained in the tubing and was introduced into the stainless drum?

That may explain the stainless corrosion. I know a lot of refiners use hand siphon pumps, the type with a small bellows on top. Those tend to hold up acid in the pipe when done siphoning. Because of that tendency I always taught refiners using those siphon pumps to keep separate pumps for each type of acid.

 

[4metals]

In other words - it stains (corrodes) less then normal iron or steel --- but that does not make it stain (corrosion) proof

I still have, 50 odd years later, the original diving knife I bought when I started diving. It was stainless steel and for a while it was shiny. Even with rinsing after every dive it now looks like something recovered from an archeological dig!