Formation of the main atmospheric zinc end products: NaZn4Cl(OH)(6)SO4 center dot 6H(2)O, Zn4SO4(OH)(6)center dot nH(2)O and Zn4Cl2(OH)(4)SO4 center dot 5H(2)O in [Cl-] [SO42-] [HCO3-] [H2O2] electrolytes

The composition of new accelerated zinc corrosion electrolytes has been der ived from the chemistry of atmospheric pollutants. Zinc plated specimens we re exposed to these solutions and the growth of the corrosion products has been studied by means of scanning electron microscopy, X-ray microanalysis and grazing incidence X-ray diffraction. First, the main atmospheric zinc e nd products were identified according to different natural environments, i. e. NaZn4Cl(OH)(6)SO4. 6H(2)O for a marine atmosphere, Zn4SO4(OH)(6). nH(2)O for a rural environment and Zn4Cl2(OH)(4)SO4. 5H(2)O developed in industri al and urban atmospheres. Then, the corrosion sequences were established fo r the 3 electrolytes able to reproduce mechanisms close to the atmospheric corrosion sequences of zinc when it is exposed to marine, rural, urban and industrial atmospheres. Accelerated corrosion tests performed in such elect rolytes would advantageously replace cyclic automobile test solutions by im proving the resemblance between accelerated corrosion results and natural o nes. (C) 1999 Elsevier Science Ltd. All rights reserved.