Boiling Temperatures of Mg Cl Solutions - Their Application in Stress Corrosion Studies

Temperatures of boiling magnesium chloride solutions used to detect susceptibility of austenitic stainless steels to stress corrosion cracking have a pronounced effect on the time to failure of these alloys. Available atmospheric boiling point data for solutions in the range 0-46 wt/% MgCl₂ have been assembled and supplemented by new experimental determinations. An equation relating boiling point and concentration for 40 to 46 wt/% MgCl₂ solutions has been derived. Because of variations in water content of reagent-grade magnesium chloride hydrate, it is proposed that measuring the boiling temperature of a solution is the preferred means both of determining the magnesium chloride concentration and of controlling this concentration during stress corrosion tests. It is further proposed that consideration be given to the general use of a 45.0 wt/% MgCl₂ solution [boiling point 155.0 C (311.0 F)] for stress corrosion tests.