Magnesium ions reinforcement

The Stability of the natural oxide film reinforced by the chromate ion determines the conditions of pH, ratio of activating anion to chromate, and temperature at which the oxide is broken down and a chromate film deposited. Thus magnesium alloys can be chromate-treated in nearly neutral solutions, whereas aluminium alloys can be treated only in solutions of appreciable acidity or alkalinity. 

The chemical corrosion resistance of AAS concrete is veiy high. The hardened paste is completely resistant to sodium sulfate, and has a very high resistance to magnesium chloride and nitrate attack (Tailing and Brandstetr, 1993). AAS concrete also protects the steel reinforcement effectively against corrosion by chloride solutions, mainly because of a very low diffusion rate of chloride ions in the hardened paste (Dhir et al, 1996). However, the carbonation of AAS concrete surfaces by the CO2 of the air progresses faster than in comparable mixes produced with Portland cement. 

Magnesinm oxychloride cement must not be combined with steel reinforcement or put in contact with steel surfaces, as chloride ions present in the pore solution and the low pH of the latter promote steel corrosion. However, magnesium oxychloride cement may be combined with glass fibers, cellulose fibers, wood chips, and a variety of other materials. Other drawbacks of this cement are poor dimensional stabihty and poor freeze-thaw resistance. 

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