Humidity Control in Accelerated Life Tests

The humidity-controlled environments over certain saturated salt solutions used for accelerated temperature-humidity life testing have been more accurately characterized. Measurements of relative humidity were made for seven salt solutions at four temperatures: 25, 50, 60, and 80°C. Variations in the experimental test environment were caused by temperature fluctuations and the approach toward uniform salt concentrations in the solutions. Establishing chemical equilibrium depends on liquid transport and requires times on the order of hours in the absence of mechanical stirring. Based on these findings improved methods for establishing atmospheres of known humidities are recommended.