Magnesium chloride mainly comes in two common commercial grades: anhydrous magnesium chloride and magnesium chloride hexahydrate. Both have magnesium chloride as the main component, but water content, physical form, hygroscopicity, cost and application scenarios are quite different.
Anhydrous magnesium chloride contains 99% MgCl₂, with almost no crystal water. It appears as white flakes or granular pellets. It is extremely hygroscopic and absorbs moisture rapidly when exposed to air. Anhydrous type is widely used for metal magnesium smelting, chemical synthesis, high‑quality flame retardant raw materials and some high‑end brine preparation. Due to strong moisture absorption, it demands strict waterproof packing and dry storage during sea shipping; caking is easy once it touches moisture. Its unit price is higher than hexahydrate.
Magnesium chloride hexahydrate carries crystal water, with MgCl₂ content around 45‑47%. Normally sold as white flakes, it is the mainstream export grade. Hygroscopic performance is much milder compared with anhydrous. Hexahydrate is popular for snow melting agent, road dust control, magnesium cement, aquaculture, coagulant for tofu processing and wastewater treatment. It is more cost‑effective and stable for regular ocean transportation, and less likely to harden under normal storage conditions.