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Magnesium Sulfate (MgSO4) Board is unequivocally more suitable for high-humidity and exterior applications than Magnesium Chloride (MgCl2) Board.

The reason is the absence of high concentrations of chloride ions in the  (MgSO4) formulation, which eliminates the core problems associated with  (MgSO4)boards in wet environments:

1. Corrosion: (MgSO4) boards are non-corrosive to metal fasteners and steel frames, whereas (MgCl2) boards can leach corrosive chloride-salt water.
2. “Weeping” / Hygroscopy: (MgSO4) boards are less hygroscopic (do not readily absorb moisture from the air) and do not exhibit the “weeping” or “sweating” of saline water droplets common with (MgCl2) in high-humidity.
3. Dimensional Stability: (MgSO4)boards maintain better dimensional stability, resisting swelling and warping when exposed to moisture and temperature changes, making them much more reliable for exterior wall sheathing or bathroom use.

For any application involving moisture exposure, such as bathrooms, kitchens, basements, or exterior sheathing, (MgSO4) (sulfate-based) is the preferred and industry-recommended choice.