Magnesium alloys possess many advantageous functional properties. Use of magnesium alloys, mainly for vehicle parts as well as electronic appliances, has been booming in recent years because of their lightweight compared to aluminum alloys and good creep resistance relative to plastics. Most the use of magnesium for structural applications has been die-cast components and most of this in one alloy, AZ91D. Since magnesium has the lowest electrochemical potential out of all the common commercial metals and is extremely prone to corrosion, it is necessary that it undergoes surface treatment. It is well known that fatigue cracks start near the free surface. Surface microstructure, therefore, should have a significant effect on the fatigue strength. This study was carried out using a mainly phosphate solution without heavy metal onto various AZ magnesium alloys. The effect of anodizing on mechanical properties and microstructure was examined by repeated tension fatigue tests, tensile tests, hardness tests and electron microscopy.