In the industrial application field, the presence of blisters in coated steel is an important quality factor of the protection coating applied on the surface. In this work, an optical system of three-dimensional reconstruction for the detection quantitative evaluation of blisters in polymer coated steel was implemented. The implemented optical system explores a region of 4 x 3 mm with a resolution of 10 μm, using the fringe projection method. The experimental evaluation was realized using six test samples of different protection coating. The test samples were continually exposed to controlled saline atmospheres and they were periodically measured. The presence of first blisters on the surface was determined. Also, the quantitative parameters were measured as maximum height and mean width of blisters, after 566 hours of exposition.