Aluminum molds are frequently used in the plastics manufacturing industry. Relative to steels, aluminum alloys offer such benefits as lower weight, improved machining and polishing, and reduced cycle time due to aluminum’s significantly higher thermal conductivity. However, corrosion within cooling water channels in aluminum alloy molds is a common challenge. Exfoliation and intergranular corrosion are the main types of attack observed. Copper-bearing alloys, such as those in the 7XXX series, are commonly used. Those alloys are particularly susceptible to exfoliation corrosion, though such corrosion can occur in other alloys as well. Factors that promote corrosion of aluminum alloys will be discussed, including microstructural features, water chemistry, and operational practices. Case histories will be presented that illustrate the exfoliation corrosion mechanism and the problems that occur in plastics manufacturing systems. Methods for control of corrosion in these systems will be proposed.
Key words: Aluminum, exfoliation, intergranular, plastics, molds