Oil & Gas pressure components found on power plants and refineries must be inspected on a regular basis to ensure fitness-for-service. Corrosion is one of the most critical and recurrent degradation that must be inspected under API-579 code. Various non-destructive methods have been used to measure corrosion. A contact method is always problematic due to the deteriorated external surface. Encoding a scan is also a challenge, requiring mechanical scanners or fixture to fit the specific component geometry for referencing the defect position. 3D laser scanning is emerging as an efficient alternative for accurate surface degradation and offers the versatility needed to inspect various geometries with a same system. The analysis is performed using post-treatment software to generate all required measurements for assessment. This paper describes how metal loss can be measured from a 3D laser mesh file compared to a reference surface. Case study of a corroded spherical pressure vessel will be discussed.