Boronizing is a thermo-chemical surface hardening process in which boron atoms diffuse into metal surface. This study investigated on boronized layer thickness of different grooved surfaces of mild steel material. Four different groove shapes were engraved on specimens that were heat-treated with boronizing process at durations 2, 4 and 6 hours and temperatures 1123, 1173 and 1223 K. The grooved surfaces were characterized and observed under microscopes to reveal the layer thicknesses for respective process duration and temperature. The results of boronized layer thicknesses were analyzed and activation energies for the boronizing process taken place at the surfaces were calculated. Different values of activation energy were determined for different grooved shapes, and this finding suggests that the surface contours affect the outcome of boronized metal surface.