The effect of surface siloxane layers on the penetration of hydrogen into iron

In acid and weakly alkaline media, including those containing hydrogenation promoters, mono- and polymolecular siloxanes layers applied to iron inhibi t both the summary cathodic process and the penetration of hydrogen into th e metal, provided the structure and thickness of the layers have been contr olled by properly chosen adsorption conditions and the chemical nature of t he starting silane. In varying the length of organic radical the decelerati on of hydrogenation correlates with the hydrophobization of the surface. Th e charge of the siloxane layer additionally strengthens or weakens the anti hydrogenating action of the layer, attracting or repelling the promoter, re spectively.