Structural damage in concrete structures caused by corrosion is widespread and demand comprehensive repair work. The additional installation of an active corrosion protective systems for structures being located in unfavourable conditions is imperative. Thermally sprayed coatings serving as anode have been adapted from the cathodic protection of steel. These systems have gained attention as they offer advantages in efficiency and lower cost. Thermally sprayed zinc coatings are applied to new steel reinforced concrete structures or those which are subject to re-structuring. In this contribution, the capability of various systems is examined by field tests in a marine structure and in different laboratory tests under natural and under accelerated conditions.

Hot dip galvanized zinc coatings on steel structures are known to have superior atmospheric corrosion resistance properties compared to painted structures. However, the zinc coating can not be applied by this method on large steel structures. The protection of large steel structures against atmospheric corrosion is traditionally done by painting. The environmental pressure to eliminate solvent based paints has forced the painting contractors to move towards water based paints or completely rethink the coating process. One solution to this problem is to use arc sprayed zinc as the "primer" and water based paints as a sealer and a top coat. The research and field tests conducted and supervised by VTT has produced promising results that are described in the paper. The possibility to apply water based paints directly over the arc sprayed zinc is discussed and results of field and laboratory tests are given. The economic aspects of both water based and traditional paint systems over the arc sprayed zinc are discussed in the paper.

Partially stabilized zirconia (8Y2O3-ZrO2) coatings were studied as thick thermal barrier coatings (TTBCs) for diesel engine applications. To improve the hot corrosion resistance of TTBCs the 1 mm thick yttria stabilized zirconia coating was densified with aluminum phosphate based sealant. Combined with better hot corrosion resistance other benefits obtained with sealing treatment are improved adhesion as well as increased mechanical properties of the ceramic layer. Three aluminum phosphate based sealants were investigated with varying viscosity level. Different sealant viscosities were used to optimize the level of sealant penetration into the coating. Sealant penetration and the violence of the reaction were determined by XRD, SEM/EDS and optical microscopy. The hardness profile from bond coat to the surface of the top layer was determined. Coating microstructure and phase structure were characterized by optical microscopy and by X-ray diffraction. Microhardness and porosity were determined. Residual stress states were measured by X-ray based stress analyzer. Bond strength of the coatings was determined with tensile test equipment. To simulate the diesel engine combustion conditions, hot corrosion tests were performed for the sealed TTBCs. Hot corrosion resistance of the coating was tested in isothermal exposure of 60Na2SO4 - 40V2O5 melt for 48 hours at 600 °C.