Corrosion Behaviors of Al-B₄C Composite Materials

The corrosion tests of Al-B4C composite materials were set in different concentrations of boric acid solution at room temperature or 40 ℃. The conductivity and pH of each boric acid solution were measured at an approximate frequency of once per three days. The solution composition changes before and after corrosion tests were tested and the changes of the specimens’ surface were compared. The corrosion of specimens is due to the aluminum. From 500 ppm to 2 500 ppm, there is a specific boric acid concentration. The corrosion rate of specimens in this solution is the slowest. The corrosion rate of specimens at 40 ℃ is faster than that at room temperature. At 40 ℃, the conductivity of boric acid solution increases with the rate of 2.25×10－2-3.23×10－2 μS/(cm•h). But the pH does not change significantly. At room temperature, the conductivity of the solution increases with the rate of 0.91×10－2-1.13×10－2 μS/(cm•h). The pH of the solution decreases 0.3-0.5. To improve the corrosion resistance of Al-B4C composite material, surface protection treatment is necessary.