A recently developed nondestructive method, called Magnetic Adaptive Testing (MAT) was applied for investigation of flake graphite cast iron samples having various metallic matrices and graphite structures. MAT is typical by its low required magnetization of samples, because it is based on measurement of families of minor magnetic hysteresis loops. The flat samples were magnetized by an attached yoke and sensitive descriptors of their magnetic/structural state were obtained from evaluation of the measured data. Conductivity measurements were performed and results of the non-destructive magnetic tests were compared with these data. A very good correlation was found between the magnetic descriptors and conductivity. Based on these results, MAT is recognized as a highly promising non-destructive alternative of destructive tests for monitoring structural changes in cast iron.