We herein report on the effect of gamma ray radiation on platinum, osmium, rhodium and palladium salt solutions for synthesis of nanoparticles. Pt, Os, Rh and Pd salt solutions were exposed to intense gamma ray irradiation with doses varying from 70 to 120 kGy. The metal ion salt solutions were easily converted into metal nanoparticles using this radiolysis method. The radiolytic conversion effect produced metal nanoparticles suspended in solution. For Pt, Pd and Rh a metal coating on the edges of the polypropylene tube used as a container was unexpectedly observed but not for the Os solution. X-Ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analyses confirmed that both the coating and the metal nanoparticles correspond to the pure metal coming from the reduction of the initial salt. Quantitative analysis of the XRD patterns shows information about the size and stress of the converted metals. The production of a metal coating on polypropylene plastic tubes by gamma ray irradiation presents an interesting alternative to conventional techniques of metal deposition especially for coating the inner part of a tube.