Newly constructed Stainless Steel Pipes experienced multiple leaks during commissioning. The different sizes pipe were constructed of 316L and 304L stainless steel at one of the Saudi Basic Industries Corporation (SABIC) affiliates. A failure investigation was performed to identify the root cause of the leaks. Samples were cut out of the pipes for analytical study. Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) was used to study the corrosion damage morphology and the chemical compositions of the corrosion products. Cross sectional samples, out of the pipes, were prepared for Metallographic examinations. XRF (X-Ray Fluorescence Spectrometry) and carbon/sulfur analyzer was used to identify the chemical composition of the pipes material. The failure investigation suggests that, improper welding, mothballing and lay-up of the piping network after hydrotesting promoted Microbiologically Influenced Corrosion (MIC).