Crack growth behavior of C110 sour gas grades was investigated during NACE Standard TM0177-2005 Method D tests in standard and mild conditions with applied direct current potential drop method. Measurements in both conditions show that the crack growth is not fully completed during the proposed test durations of 14 and 17 days, respectively. Sufficient test durations of 10 days in both conditions were determined where crack growth has no significant influence on the obtained stress intensity factors KISSC in sour gas conditions. Furthermore different alloying concepts and heat treatments were investigated towards sour gas resistance of C110 grades. Higher annealing temperatures and plate-shaped martensite microstructures enable best sour gas results.