The susceptibility to reaction with solid and liquid aluminum of TiN and (Ti,Al)N coatings was investigated using complementary differential scanning calorimetry and X-ray diffraction. Special freestanding, multilayered thin film structures of aluminum and the testing coating material were prepared for the calorimetric analyses. The results indicate that increasing concentrations of Al in the (Ti,Al)N compound coatings shift the reactions between coating and aluminum towards higher temperatures, reducing significantly the heat of reaction and inhibiting Al-Ti intemetallic compound formation. Different effects determining the protective action of this kind of coating are discussed on the basis of the present findings, together with others from the literature. Aluminum-rich Ti1-xAlxN compound coatings, with x ranging from 0.6 to 0.7, are apparently inert (non-wettable) in the presence of aluminum up to 1000 degrees C, a temperature high enough to resist any known aluminum casting situation. (c) 2007 Elsevier B.V. All rights reserved.