| 摘要 |
Compounds of the formula <IMAGE> I in which X is -S-, -O- or -NH-, R is H or a monovalent substituent, n is 0 or 1 and R1, R2, R3 and R4 are H, alkyl, alkyl which is substituted by OH, halogen, COOH or alkoxy, unsubstituted or substituted aryl or aralkyl, or carboxyl, or R1 and R2 or R1 and R3 together are alkylene or R1 and R2 are a direct bond, at least two of the groups R1, R2, R3 and R4 being carboxyl or carboxyalkyl groups, and base addition salts thereof are effective corrosion inhibitors. The preparation of these novel polycarboxylic acids can be effected by various processes.
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