Laboratory Solutions for Studying Corrosion of Aluminum Alloys in Seawater

The difficulties in obtaining reproducible results for the corrosion of aluminum alloys in saline waters, both in the laboratory and in the field are well known. The various factors contributing to variability in aluminum corrosion data in saline waters are briefly reviewed. This information is then used to evaluate NaCl solutions, enhanced NaCl solutions, synthetic seawaters, and stored seawater as substitutes for natural seawater in studying the corrosion of aluminum in the laboratory. The effects of such factors as dissolved oxygen concentration, pH, temperature, organic content, salinity, and stability of the solution are discussed. While no laboratory solution can replace natural seawater for long-term corrosion testing, an artificial solution composed of sodium chloride, sodium bicarbonate, and magnesium, with controlled oxygen, pH, temperature, and hydrodynamics is suitable for many laboratory purposes. This solution is simple, more stable than either natural or artificial seawater, and closely reproduces the short-term behavior of aluminum alloys in natural seawater.