![]() Alloys with nickel contents above 35% are highly resistant and alloys above 45% are nearly immune. The greatest susceptibility is at a nickel content of 8% to 12%. Nickel content of the alloy has a major affect on resistance. Oxygen dissolved in the water normally accelerates SCC but it is not clear whether there is an oxygen concentration threshold below which chloride SCC is impossible. Highly stressed or cold worked components, such as expansion bellows are highly susceptible to cracking. Cracking usually occurs at metal temperatures above about 140F, although exceptions can be found at lower temperatures SCC tendency decreases toward the alkaline pH region. At lower pH values, uniform corrosion generally predominates. SCC usually occurs at pH values above 2. Alternate exposures to wet-dry conditions or steam and water are also conducive to cracking. Heat transfer conditions significantly increase cracking susceptibility because they allow chlorides to concentrate. No practical lower limit for chlorides exists because there is always a potential for chlorides to concentrate Increasing lebels of chloride increase the likelihood of cracking Increasing temperatures increase the susceptibility to cracking Chloride content, pH, temperature, stress, presence of oxygen and alloy composition are critical factors
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