الفهرس Only 14 pages are availabe for public view
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Abstract
An anodizing process, based on environmental friendly electrolytes
solutions that contains none of chromate, phosphate or fluoride has been
studied by using three types of electrolytes: the first is based on sodium
silicate, the second on sodium hydroxide- Boric acid- Borax and the
third on sodium silicate- potassium hydroxide- sodium carbonatesodium
tetra borate. Two type of Pretreatment process commonly used
in electroless processes and zinc immersion including fluoride
activation has been applied before the anodizing process. Anodizing
behaviors of AZ 91magnesium alloy are influenced by many factors,
including the constituents of electrolyte solution, applied current density
or voltage, and deposition time. It is found that the anodic film
thickness increases as current density or anodizing voltage increases
with deposition time until the deposition stops due to the formation of a
thick anodic film. The increase in the film thickness is not always linear
with increasing current density and deposition time. Optimization of the
anodizing conditions - current density and deposition time - was made
based on the maximum thickness obtained. Characterization of
anodizing layer was achieved by determination of surface morphology,
microstructure, phase analysis, coat thickness, adhesion and corrosion
resistance.
For all electrolytes, excellent adhesion and corrosion resistance was
obtained with a corrosion efficiency ranging from (94%-97%).