Definition - What does Sodium Sulfate mean?
Sodium sulfate (Na2SO4) is a chemical compound that can be found as a mineral in nature or derived from certain industrial processes as a byproduct. It has many commercial applications, and is classified as a non-toxic chemical under normal handling circumstances.
Sodium sulfate is commonly used to make soaps and detergents, particularly powdered soaps. It is also used to make textiles, in the production of paper and paper pulp, in glass production, and a variety of other applications.
Sodium sulfate also used as a backfill material in cathodic protection.
Corrosionpedia explains Sodium Sulfate
Sodium sulfate is the sodium salt of sulfuric acid. When anhydrous, it is a white crystalline solid of formula Na2SO4 known as the mineral thenardite. Sodium sulfate is one of the most important minerals in the chemicals industry.
Sodium sulfate is chemically very stable, being nonreactive toward most oxidizing or reducing agents at normal temperatures. At high temperatures, it can be converted to sodium sulfide by carbothermal reduction. It causes hot corrosion, which is the degradation of materials caused by the presence of a deposit or ash, predominantly sodium sulfate. Hot corrosion is observed in marine and aircraft engines. It is very well established that sodium sulfate alone causes accelerated oxidation of super alloys and coatings at high temperatures, where Na2SO4 is in liquid form.
It is generally believed that the molten sodium sulfate deposit is required to initiate a hot corrosion attack. The temperature range for a hot corrosion attack, although dependent on alloy composition, is generally 1470 to 1740°F (800 to 950°C).
Sodium sulfate is a strong contributor to the rate of corrosion. For example, in water with 400 mg/l of alkalinity (as calcium carbonate) at pH 7, the corrosion rate is zero at 200 mg/l of Na2SO4, but when the concentration of sodium sulfate is 400 mg/l, the corrosion rate is about 100 mg per square cm per day.