Each of these iso-corrosion diagrams was constructed using numerous corrosion rate values,
generated at different acid concentrations and temperatures. The blue line represents those
combinations of acid concentration and temperature at which a corrosion rate of 0.1 mm/y (4
mils per year) is expected, based on laboratory results. Below the line, rates under 0.1 mm/y
are expected. Similarly, the red line indicates the combinations of acid concentration and
temperature at which a corrosion rate of 0.5 mm/y (20 mils per year) is expected. Above the
red line, rates of over 0.5 mm/y are expected. Between the blue and red lines, corrosion rates
are expected to fall between 0.1 and 0.5 mm/y. The iso-corrosion diagram for hydrofluoric
acid should be used with caution. Internal attack of nickel alloys is common in this acid; thus
field tests prior to industrial use are even more important. Also, while HYBRID-BC1 alloy
possesses useful resistance to nitric acid, stainless steels are generally preferred to nickel
alloys in pure nitric.