... cert 4,quick delivery constrution use hot dip galvanized square and rectangular steel pipe/SHS/RHS 1. Outer diameter:20*20-400 ... treatment: bared, galvanized, oiled, painted to prevent rust.5. Technique: ERW, hot-rolled6. Certification: CE, ISO7. Material: Q195, Q235, Q345( ... , for instance, steel construction project, machinery making and shipbuilding.structural square tube OD(mm)WT(mm)OD(mm)WT(mm)20 ...