Corrosion Resistance in Sea Water Of Medium Strength Aluminum Bronzes

The corrosion resistance of aluminum bronzes of the 90/10 type is good, providing eutectoid decomposition of the beta phase to alpha + gamma₂ is prevented. If gamma₂ is present, it is highly anodic to the alpha matrix and rapid corrosion will occur. Retention of beta is favored by a fast cooling rate and a high manganese content. Nickel and iron are of less significance and the effect of aluminum is dependent upon the percentages of other elements present. In general, however, beta retention is favored by a low percentage of aluminum. Silicon additions give rise to a close-packed-hexagonal kappa phase which is not easily decomposed to alpha + gamma₂. The result is that the microstructures of certain Cu-Al-Si alloys are less sensitive to cooling rate; hence, a reliable corrosion resistance is more easily obtained.