Corrosion in pipes is a problem faced in several domains, like the oil and gas or nuclear industries, due to the risk of rupture or leakage. Non-Destructive Testing (NDT) techniques using elastic guided waves have proven useful to detect such defects due to their ability to interrogate large structures and their sensitivity to defects. More recently, Structural Health Monitoring (SHM) approach seeks to implement permanently attached sensors over the structure lifetime. Elastic guided waves tomography can reconstruct a thickness map of the structure over a large zone with a reduced number of transducers, and thus localize and characterize corroded areas. Tomographic algorithms are well suited for a passive approach, without wave excitation. In that case, sensors only measure the ambient elastic noise present in the operating structure (due to flow, vibrations…). The cross-correlation of these signals allows getting the same information as with measurements from active sources. Passive process has been demonstrated in plate-like structures. This paper shows experimental results of corrosion imaging in pipes using passive tomography. The passive approach is a path forward for using optic fibers with Fiber Bragg Grating (FBG) instead of piezoelectric transducers, offering a lighter, less intrusive and more permanent solution.