Inconel 600 and 800...unexpected corrosion

[prmmel]

I have an application where we have a quench scrubber before a tower. The temperature probe between the quench and scrubber is Inconel 600 and after about 1 week, it looked sandblasted and came apart. The operating temp is about 120-175F and no higher. The quench water will have relatively low concentrations of about 500-1000ppm of HCL and chlorides. We also have a hastelloy quench nozzles that is connected to the tower by a piece of Inconel 800 tubing. This inconel tube and hastelloy sees about 700F and is where mist is injected as quench cooling water.

We did not expect either of the Inconel components to fail, but they did rapidly. Now, after doing some research, I find that there is the possibility of Permanganate in the stream. I am seeing some inf on the net that Permanganate may react. Any suggestions on the Inconel failure and if you would expect this?

Switching to Hastelloy next week, but really would like to understand for future reference.

 

[unclesyd]

Which permanganate salt do you have or is it permanganic acid?

One thing that is a little puzzling is that there wsre no problems with the Hast C in the presence of an oxidizer. A cursory look at my data doesn't light up nay neurons. Will look some more.

 

[prmmel]

It appears that it is KMnO4 (Potasium Permanganante. In reading online, I see several references that show Inconel corrossion with mild amounts of KMn04 in the stream. FYI, the hastelloy is not exposed to the Sodium Hydroxide solution.