Abstract: Analyzed is the cause for the unsatisfactory bonding of the LLDPE coating with the inner galvanized surface of the hot-galvanized steel pipes under DN100. The respective advantages and disadvantages of the two pre-coating treatment processes for the inner surface of the said pipes are compared, based on which result, the said chronic technical problem concerning the LLDPE bonding is fixed by means of special phosphorization of the pipe prior to the plastic coating. It is concluded that thanks to the said solution, only small investment needs for hot-galvanized steel tube makers to produce hi-efficiency and health-friendly water pipes for antiearth quake high-rise buildings.