Gravimetric investigation of corrosion processes in chloride melts

2 Gravimetric investigation of corrosion processes in chloride melts 

The low depth of the IGC in AISI 316L steel can be explained by the low carbon content, resulting in the formation of a discrete carbide chain along the grain boundaries. In the AISI 321 and 316Ti types of steel with 

The above-mentioned sensitization effect and subsequent IGC can explain the changing chromium concentration in the melt. Due to sensitization, chromium is initially consumed by the carbide phases formed and the concentration of this element in the surface layer of grains decreases. Prolonged contact of steel samples with 

Chromium concentration near the grain borders can be as low as 8 -10 wt%, that is, below the limit that ensures the corrosion resistance of steel [22], The presence of an electrolyte, in our case fused chloride mixture, leads to the formation of microgalvanic elements and selective corrosion of zones depleted in chromium. For this reason the IGC is spread only along the zones adjoining boundaries of grains depleted in chromium. 

The following mechanism of stainless steel corrosion in molten chlorides can thus be proposed. At the first stage a chemical exchange reaction between the alloy and the salt takes place. This interaction results in a gradual etching of samples. The rate of corrosion in the initial moment of time is highest due to a significant difference between the values of the red-ox potentials Me /Me a /A where Me is a component of steel 

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