Lock seam perforated pipe is made by folding up the overlapping edges against each other, then folding them over in the same direction a number of times. It has flush surface outside and lock seam inside. This type perforated tubing is the popular option of fluid filtration like center tube in the filter house.
Mild steel and stainless steel are common materials of manufacturing spiral perforated tubes. For generally applications, carbon steel is available to serve. However, for corrosive work conditions, stainless steel perforated pipe is a cost-efficient choice in the long terms.