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In this study, erosion tests were conducted to evaluate the behavior of AISI 420 against walnut particles. This organic material was selected to evaluate its performance as abrasive particle and know if this 'soft abrasive' could really cause any damage on the material surface. The interest on walnut shell grit arose because this is extremely durable, angular and can be reused several times in many applications. Walnut producers have indicated that this can remove matter from surfaces without scratching or pitting underlying material. However, in this work, wear mechanisms similar to those observed when hard abrasive particles are used for erosion testing, were identified. SEM photographs showed micro-cutting (scratches) and micro-ploughing actions and particles embedded on the surface of AISI 420. In fact, this latter mechanism affected considerably the erosion rates at all incident angles. Finally, AFM technique and surface profilometry were employed to obtain the wear scar profiles to show the degradation of the surfaces by the impact and sliding actions of the walnut particles. [ABSTRACT FROM AUTHOR]