Thin black films composed of bismuth and respective iodides, i.e. CuI and AgI can be produced upon an immersion of copper or silver substrates into KBiI4 solutions. The reactions leading to the formation of black films onto copper or silver surfaces into KBiI4 solutions are spontaneous at the standard physico-chemical conditions, as evidenced by the thermodynamic data. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.esl113444] All rights reserved.