Corrosion Behavior and Morphology of Passive Films Modified with Zinc–Aluminum Simultaneous Treatment on Different Metals
Round 1
Reviewer 1 Report
In my opinion, the paper requires a major revision. To improve this work the Authors should take into account the following comments:
Line 95-104: what was the dimension of the Pt electrode? The statement “-0.5 V ~ 1 V” is inconsistent with Figure 1. What was the amplitude of the ac signal in EIS measurements? How many points per decade were used in EIS measurements? What was the frequency used in Mott-Schottky analysis?
Line 114: Authors should explain precisely how the values of corrosion current density and corrosion potential were “calculated”. What was the range for cathodic and anodic branch?
Line 117 (Table 3): what was the measurement uncertainty for corrosion current density?
Line 124: Authors should discuss Ecorr values as well.
Line 135-137: appropriate equivalent circuit should be chosen based on the mechanism of the investigated electrochemical process. Thus, this sentence should be corrected.
Line 142: the equation for constant phase element should be given. Y in CPE is equal to capacitance only for n=1. For n≠1 Brug equation should be used for estimation of double-layer capacitance. Thus, this sentence should be corrected.
Line 153 (”…was controlled by electrochemistry”): this statement is unclear and should be revised.
Line 162 (Table 4): Authors should explain Warburg impedance obtained for A508-3 G(blank) and A508-3 G(Zn). According to Authors “The inner layer is a dense protective oxide film … and the outer layer is a loose protective film – line 147-148” however for all materials Qin >> Qout? Authors should explain this.
Line 163 (Figure 3): fits obtained for A508-3 steel are very poor. Is the equivalent circuit appropriate for A508-3 steel?
Line 170: Authors should explain precisely how the values of space charge capacitance were determined using the EIS technique.
Line 174 (Equation 1): there is a lack of surface area in the Mott-Schottky equation. Why? The discussed slope of M-S straight lines depends on surface area and dielectric constant. Whether these parameters are the same for all oxides tested? Values of dielectric constant, Efb and N should be given. Moreover, the fit of straight lines should be shown in Figure 5.
Figure 6-15: what was the measurement uncertainty for chemical composition?
Line 322 (”the smoothness of the surface of passive films”): Authors should determine the roughness factor RF for investigated electrodes. RF can be calculated based on double-layer capacitance values estimated from EIS measurements. Such discussion may clarify the influence of active surface on corrosion resistance and complement SEM examinations.
Author Response
Dear Reviewer:
Thank you very much for giving us an opportunity to revise our manuscript, we appreciate for your efficient work and constructive comments on our manuscript.
The comments from you are adhesive in attachment. We answer the comments one by one in a different font. And the changing in the revised manuscript is highlighted by using the track changes mode. And, it should pay attention that, several Figures, Equations and References of this manuscript are changed according to other reviewers’ report.
In addition, the English of this manuscript had been edited by professional English editing service.
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this paper, the different materials as Alloy 508-3 steel, 304L 61 stainless steel, and Incoloy 800 nickel alloy films were modified by the zinc treatment and zinc-aluminum simultaneous treatment at 300 °C, respectively.
The Authors present interesting results. However, due to the fact that materials behave very differently during the processes described, it is difficult to provide a clear conclusion regarding the recommended and optimal treatment of materials.
- Nevertheless, I am asking the authors to elaborate on this point in their conclusions.
- In addition, the chapter on the methodology lacks specification of the experimental apparatus, and also the measurement parameters used in the experiments.
- With regard to the results of the SEM microstructure analysis:
- what type of microscope was used for testing,
- the oxygen percentage is usually obtained with a very large measurement error, therefore it is important to provide the technical parameters of the scanning microscope and to provide measurement uncertainties.
- given the presence of inclusions and precipitates in SEM microstructure images, it would be reasonable for complete characterization, to perform a surface distribution of the elements or/and to examine the chemical composition of points rather than averaged from a large area.
Author Response
Dear Reviewer:
Thank you very much for giving us an opportunity to revise our manuscript, we appreciate for your efficient work and constructive comments on our manuscript.
The comments from you are adhesive in attachment. We answer the comments one by one in a different font. And the changing in the revised manuscript is highlighted by using the track changes mode. And, it should pay attention that, several Figures, Equations and References of this manuscript are changed according to other reviewers’ report.
In addition, according to your suggestion, the English of this manuscript had been edited by professional English editing service.
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper presents several experimental results related to the corrosion behaviour of passive films based on zinc and zinc-aluminum treatments in air at 300 °C formed on several alloy substrates, respectively on A508-3 steel, 304L stainless steel and Incoloy 800.
The authors applied several electrochemical techniques to assess the corrosion performance, including potentiodynamic polarization, EIS and Mott-Schottky. SEM and EDS have been used to get information on the passive layers morphology and composition.
While some aspects are quite interesting, several recommendations have been proposed and should be considered before publication. They have been detailed in the annexed document.
Moreover, the English is strongly recommended to be re-checked, especially for formulations according to the technical style.
Comments for author File: Comments.pdf
Author Response
Dear Reviewer:
Thank you very much for giving us an opportunity to revise our manuscript, we appreciate for your efficient work and constructive comments on our manuscript.
The comments from you are adhesive in attachment. We answer the comments one by one in a different font. And the changing in the revised manuscript is highlighted by using the track changes mode. And, it should pay attention that, several Figures, Equations and References of this manuscript are changed according to other reviewers’ report.
In addition, according to your suggestion, the English of this manuscript had been edited by professional English editing service.
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
In my opinion, the paper requires minor revision.
Line 162 - Table 4 (description from the first version of manuscript): The point of question “Authors should explain Warburg impedance obtained for A508-3 G(blank) and A508-3 G(Zn)” was that in Table 4 n=0.553 for A508-3 G(blank) / Qout and n=0.593 for A508-3 G(Zn) / Qout. Both n values are close to 0.5 (they are closer to 0.5 than to 1) what indicate Warburg impedance and not capacitive reactance. Please check this.
Table 6: in row ”Group” there is “In800” twice. It should be corrected.
Author Response
Dear Reviewer:
Thank you for your efficient work and constructive comments on our manuscript. The comments from you are adhesive below. We answer the comments one by one in a different font. And the changing in the revised manuscript is highlighted by using the track changes mode.
Point 1. Line 162 - Table 4 (description from the first version of manuscript): The point of question “Authors should explain Warburg impedance obtained for A508-3 G(blank) and A508-3 G(Zn)” was that in Table 4 n=0.553 for A508-3 G(blank) / Qout and n=0.593 for A508-3 G(Zn) / Qout. Both n values are close to 0.5 (they are closer to 0.5 than to 1) what indicate Warburg impedance and not capacitive reactance. Please check this.
Response 1. As you pointed out, the n value of Qout (close to 0.5) in G(blank) and G(40Zn) of A508-3 indicated that the outer layer of the passive films formed on A508-3 with blank treatment and zinc treatment were close to the Warburg impedance caused by semi-infinite diffusion, and the concentration polarization existed on the surface of passive film formed on A508-3. We have added these descriptions in this section following your comment. （Line 199-202)
Point 2. Table 6: in row ”Group” there is “In800” twice. It should be corrected.
Response 2. We are sorry for our mistake. In row "Group", the second column of Table 6 should be "304L". We have corrected it. (Tabke 6)
Reviewer 3 Report
The authors have made all recommended corrections.
Author Response
Thank you for your efficient work and constructive comments on our manuscript.
