Corrosion inhibiting composition

A composition, in contact with a corrodible metal surface, which composition comprises:

• a) an aqueous-based or oil-based system;
• and
• b) as inhibitor for protecting the metal surface against corrosion, an effective amount of at least one compound having the formula II:
• ##STR9## as well as salts or partial esters thereof wherein:
• n is 0 or an integer ranging from 1 to 20,
• R is a straight or branched chain C.sub.4 -C.sub.30 alkyl group, a straight or branched chain C.sub.4 -C.sub.30 alkyl group interrupted by one, two or three oxygen atoms or substituted by one, two or three hydroxy groups, a C.sub.5 -C.sub.12 cycloalkyl group, a C.sub.6 -C.sub.10 aryl group, C.sub.6 -C.sub.10 aryl group substituted by one, two or three C.sub.1 -C.sub.12 alkyl groups, a C.sub.7 -C.sub.13 aralkyl group or a C.sub.7 -C.sub.13 aralkyl group which is substituted by a hydroxyl group;
• R.sub.1 is H or a straight- or branched chain C.sub.1 -C.sub.4 alkyl group;
• R.sub.2 is H, a straight or branched chain C.sub.1 -C.sub.4 alkyl group or CO.sub.2 H;
• R.sub.3 is H, a straight or branched chain C.sub.1 -C.sub.4 alkyl group, --CH.sub.2 CO.sub.2 H or --CH.sub.2 CH.sub.2 CO.sub.2 H;
• R.sub.4 is H, a straight or branched chain C.sub.1 -C.sub.4 alkyl or CO.sub.2 H;
• R.sub.5 is H, a straight or branched chain C.sub.1 -C.sub.4 alkyl group, CH.sub.2 CO.sub.2 H or CH.sub.2 CH.sub.2 CO.sub.2 H;
• with the following proviso
• when n is an integer from 1 to 20 at least one group R.sub.4 is CO.sub.2 H.