  We demonstrate the imaging of ferromagnetic carbon steel samples and we
detect the thinning of their profile with a sensitivity of 0.1 mm using a Cs
radio-frequency atomic magnetometer. Images are obtained at room temperature,
in magnetically unscreened environments. By using a dedicated arrangement of
the setup and active compensation of background fields, the magnetic
disturbance created by the samples' magnetization is compensated.
Proof-of-concept demonstrations of non-destructive structural evaluation in the
presence of concealing conductive barriers are also provided. The relevant
impact for steelwork inspection and health and usage monitoring without
disruption of operation is envisaged, with direct benefit for industry, from
welding in construction to pipeline inspection and corrosion under insulation
in the energy sector.
