The protection of condensing boiler surfaces is a very important issue for the industry. The use of latent condensing heat significantly increases the efficiency of the boilers, but causes problems due to the corrosive nature of the condensates, mainly due to SOx in the flue gases which condense to form H2SO4. The CVD-ALD laboratory is exploring the potential of CVD-deposited WCxOy films. Specifically, the use of ultra-thin films is investigated so that a) the coefficient of thermal conductivity is not significantly reduced, and b) they enhance the condensation in drops and the outflow of the condensates and therefore have an increased heat transfer coefficient. As part of a funded program (ECODROPDENSER) the functionality of these coatings is evaluated for energy in a commercial boiler.