Fig. 7 was the curve of B4C composite ceramic quality change rate in simulated seawater, which showed its quality losses began to increase with corrosion time and then appeared a peak in the 7th day. Finally the quality loss rate decreased. The curve of quality change rate in different time was small in all corrosion process and the maximum quality change rate was only 1.31×10-2 mg×cm-2 ×d-1.