In the petroleum industry wellbore integrity is one of the most important tasks. One of these elements is wellbore cementing and the interface between cement and the casing respectively cement and rock. This Master Thesis deals exactly with those interfaces, because only with intact bonding’s between cement / steel and cement / rock wellbore integrity can be given. The bond interface can easily be damaged due to several wellbore operations in drilling like POOH, RIH, fishing reaming or free stuck pipe when jarring is done. During all these Operations the bond is mainly stressed with shear loads. In this Thesis, several shear tests with cement and steel and cement and rock were conducted In most of the cases, wellbore leakage is because of bad or faulty cement jobs between cement / casing and cement / rock. On one hand side it is possible that formation water which has a very high salinity can migrate through micro channels and micro annuli through the cement and react now directly with the surface of the casing and corrodes it. When casing leakage happens it is definitely possible that several formation fluids can flow behind the casing into other formations, or even the worst case, a flow of formation fluids into the ground water. To get more information about the bonding strength between cement / steel and cement / rock, several shear test with steel plates with different surface roughness’s and different rock types with and without saltwater saturation were done. All these tests may help to improve wellbore integrity and were documented and published in this thesis.