Detecting the Corrosion of a Steel Rebar Using the Eddy Current Testing Method

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Good manuscript, in general. I suggest addressing the following questions and comments before its publication:

·       What criteria, if any, was used for selecting the diameters of coils?

·       It is, in fact, the depth of the rebar from the probe that affects the signal. Although the depth increases with increase in concrete thickness, the measuring parameter should be ‘depth of the rebar’ rather than ‘thickness of the concrete’. The data presented should clearly indicate the depth of the rebar for each concrete thickness, especially on figures on page 11 and 14. The figure on page 14 is numbered incorrectly.

·       The diameter of one of the coils in Sections 3.1 and 3.2 is 7 cm, whereas it is stated as 8 cm in Section 3.3. Please clarify if those are two different coils.

·       Signals in Figures 6, 9, 10 and 15 should be shown on the same scale for ease of comparison of amplitude and phase. It is a common practice to present the eddy currents signals in four quadrants with center of the signal lying at the origin and using similar scales on the x and y axes.

·       It is stated on page 2 (Table 1 and Line 84) that the permeability of Fe3O4 could be several hundred. A reference should be added to support this statement.

·       Line 107: Check the units of current noise.

·       Some information in Section 3.2 is already given in Section 3.1. Repetition should be avoided.

·       Line 40: Delete ‘of the detection’.

·       Line 80: Probably the words ‘magnetic conductivities’ need to be deleted.

·       Line 103: It should be ‘detection coil’.

·       Line 191: The words ‘excitation coils’ should likely be ‘detection coils’.

Comments on the Quality of English Language

English is of acceptable level. Some typos and fragmented sentences are mentioned in the comments above.

Author Response

Please see the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript develops a portable eddy current system for detecting steel rebar corrosion, optimizing coil design and excitation frequency for improved performance. The study demonstrates the advantage of differential detection coils. However, some points need detailed elaboration.

1. How do other parameters, such as environmental variability (e.g., temperature, humidity) and differences in concrete composition and steel rebar alloys, affect the detection results?

2. Does the shape of the rebar influence the results? Specifically, how are the results affected by rebars with surface features, such as knots or ridges?

3. In Figure 6, why does the curve slope change as the excitation frequencies increase? Additionally, why is the first curve marked in red?

4. It is evident that the differential coil system outperforms the toroidal one. However, the explanation in the Discussion section lacks clarity. Can the authors provide a more detailed elaboration?

5. How scalable is the system for applications in larger structures or for continuous monitoring in complex environments, such as multi-layer rebar grids?

6. Regarding the corrosion degree of steel rebar, can the authors provide further insights or metrics for its quantification?

Reminder: the final figure should be labeled as Figure 16, not Figure 12. Please verify and correct this in the manuscript.

Author Response

Please see the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The revised manuscript is in much better shape now. I recommend its publication.