MULTI-SPACING ARRAY TOOL

Systems and methods to investigate multi-pipe structures for detection of corrosion and quantitative assessment of thickness in the multiple pipes can be implemented in a variety of applications. Systems can include a set of transmitters and multiple receivers arranged on a tool structure with variable distances to the transmitters of the set of transmitters, where the receivers are arranged to measure electromagnetic responses from a multi-pipe structure to excitation of the set of transmitters with the tool structure disposed in the multi-pipe structure. The electromagnetic responses may include responses correlated to a near field zone, a transition zone, and a far field zone, where the electromagnetic responses can be processed to recover individual thicknesses of each pipe of the multi-pipe structure. Additional apparatus, systems, and methods are disclosed.