Experiments on the improvement in durability of pipe framework for plastic greenhouse were carried out. Effect of protection treatment such as primer and paint coating for new pipes and old rusted ones were evaluated by change of rusty degree and yield strength. The experiments have been conducted during five years until now but it was too short to find the clear differences. However, there was a little improvement in durability of greenhouse pipes by painting after removal of rust. And also component and corrosion characteristics of pipes being used in greenhouses were analyzed, and several countermeasures for protection from corrosion were reviewed.