**2. Test materials**

The chemical composition of test alloys was analysed using spark emission spectroscopy. The typical composition (by weight) of both Hercules™ alloys is:

**Figure 6.** *The general microstructure (scale bar 20* μ*m) of Hercules™ a (left) and Hercules™ b (right).*

*The Evaluation of the Comparative Corrosion Behaviour of Conventional and Low-Nickel… DOI: http://dx.doi.org/10.5772/intechopen.102381*

2% Ni, 16% Cr, and 10% Mn and 0.25% N, with a difference on Mo content where Hercules™ A (no Mo addition) and Hercules™ B (0.5% Mo). The test samples were in the hot rolled and annealed condition, while 304SS (8%Ni, 18%Cr, 1.8%Mn, 0.03%N) was commercially received.

**Figure 6** shows the general microstructures of Hercules™ alloys. Grinding, polishing and etching of the sample surface was performed in order to reveal the microstructural features. The Beraha tint etchant was used to colour and highlight the twin boundaries white and the prior austenitic grains brown. The microstructural evaluation showed that Hercules™ alloys have fully austenitic microstructure with an insignificant amount of ferrite (etched dark spots) dispersed on the austenite matrix at room temperature.
