Hastelloy C-276 Chemical Reactions

[usjbh]

I have sintered H C-276 filter disks undergoing chemical compatibility soak tests in some 30 different solvents and chemicals. The 6M Nitric acid test solution turned a light green coloration after one hour exposure then turned light blue after 3 hours. One week later the blue color is getting a little bit darker. I suspect the intial green coloration may be due to a reaction initially from the Cr-15% (Yellow) and Mo-16%(Blue)with the Mo ultimately taking over. Additionally, after one week exposure in 20mM Sulfuric Acid there is a light blue discoloration of the acid taking place with another test disk. Can anyone explain my observations? Is there an explaination why this HC-276 sintered item is so reactive in 6M HNO3?

 

[unclesyd]

It is very basic.

Hastalloy C isn't compatible in varying degrees with oxidizing chemicals and HNO3 is one of the better oxidizers.

Additionally your Corrosion rates will mean very little where you have a high rate of corrosion if a metal in finite volume of corrodent. In you case it is further skewed by the surface are to liquid ratio.