The citric acid does not eat metal. Actually, it neutralizes the scale and calcium carbonate of the mineral deposits which were part of hard water used in the radiator. The word citric comes from the Latin word, and is similar to the French and Spanish words, "citron". But it is not similar to the Hungarian word.
As a natural fruit acid, it cannot dissolve metal. It will, however, keep your cooling system clean of mineral deposits. If you liked the lemon-smelling dishwater soaps, you'll love this MB product.....Andras