The present invention relates to a method for reducing or preventing the formation or activity of a corrosion-associated biofilm on a metal surface, wherein the method comprises contacting the metal surface with a liquid composition comprising biocidal preparation. The present invention also relates to a microbicidal composition comprising at least one alcohol, one liquid hydrocarbon, a bacteriophage immobilized on a magnetic nanocomposite, at least one phage releasing reagent and one stabilizer. The microbicide composition and method of the present invention reduces biofilms on surfaces, and consequently, reduces, mitigates, or eliminates MIC in internal surface of the oil transporting pipelines.