A metal cleaning composition is provided comprising: a nonionic active agent and/or an anionic active agent having an HLB value ranging from 3 to 18; and a carboxylic acid or salt thereof represented by the formula, [equation included]
in which X represents N--H, N(CH.sub.2).sub.n --COOM or CH--COOM, R represents a saturated or unsaturated aliphatic hydrocarbon group having from 4 to 18 carbon atoms, phenyl group or tolyl group, and M represents a cation; and a five-membered ring compound having either one nitrogen atom and one sulfur atom, or three nitrogen atoms, and/or a quinoline derivative having a hydroxyl group.
The composition according to the invention is advantageous in washing steel or copper plates without inducing pitting corrosion on the metal surface being contacted therewith.