Dezincification rates of α- and β-brass were measured by a thermo-gravimetry over the temperature range 500–800°C in vacuum. The results were discussed in connection with a structural change in the diffusion layer, that is, formations of voids and cracks. The dezincification reaction proceeded through three stages. In stage I, the weight loss obeyed the parabolic rate law as expected from an ordinary diffusion mechanism. In stage II, the dezincification rate was accelerated. In stage III, the weight loss was nearly proportional to the square root of time. These three stages were characterized by the amount of structural change.
In α-brasses, the reactions can be classified into three types depending upon the zinc content; reaction proceeded (1) only by stage I, (2) by stage I and stage II, and (3) by stage I through stage III. Type (3) was observed only in the specimens with higher zinc contents during dezincification at higher temperatures.
In β-brasses the reaction started from stage II and reached stage III.
The dezincification process of brasses with both α- and β-phases, approached that of β-brass as the zinc content increased.