Pinhole-free diamond layers can widely be used in sensor technology as resistive coating against electrolyte solutions. The diamond layers created with chemical vapour deposition technique (CVD) are pinhole-free only above a certain thickness (at least 2.4 mu m). Such layer thicknesses reduce the application possibilities. On the other hand, thin (similar to 200 nm) diamond like carbon (DLC) layers deposited by pulsed laser deposition technique (PLD) are pinhole free but have adhesion or contiguity problems depending on layer thickness. Utilizing the advantages of these two techniques a combined method was developed in order to prepare a pinhole free thin diamond-DLC double layer, for corrosion protection coating. The effects of various deposition parameters (such as background gas, temperature, bias, layer thickness) on the protective properties of the layers have been studied. (c) 2006 Elsevier B.V. All rights reserved.