Investigation on Corrosion Resistance and Formation Mechanism of a P–F–Zr Contained Micro-Arc Oxidation Coating on AZ31B Magnesium Alloy Using an Orthogonal Method
and Yijia Zhang 1Round 1
Reviewer 1 Report
Paper presents the study of the influence of electrolyte composition used for microarc oxidation of magnesium alloy on morphology, composition and corrosion properties of formed coatings. Manuscript is well organized and suitable for publication in present form.
Author Response
We highly appreciate your carefulness, conscientious, and the broad knowledge on the relevant research fields.
Reviewer 2 Report
The present work involve the study of the influence of differetn compunds on the corrosion resistance of PEO coatings. The work is interesting and quite new but there are a lot of issues that have to be resolved before publication.
1) The main issue is the quality of the presentation and the english. The article is in a lot of parts difficult to understand (for example lines 178-196, 230-239, 252-256 and also other). Morehover also the structure of the work is unclear there are too much subparagraph and is very difficult to understand the logic of the work. I suggest to revise the structure condensing some parts.
2) I suggest a bit more bbiliographic research oin biocompatible and antibacterial PEO coatings (see for example the works Cerchier P, Pezzato L, Brunelli K, Dolcet P, Bartolozzi A, Bertani R, Dabalà M Antibacterial effect of PEO coating with silver on AA7075, Mater Sci Eng C Mater Biol Appl. 2017 75:554-564, Mohedano M, Guzman R, Arrabal R, López Lacomba JL, Matykina E. Bioactive plasma electrolytic oxidation coatings--the role of the composition, microstructure, and electrochemical stability J Biomed Mater Res B Appl Biomater. 2013 Nov;101(8):1524-37)
3) Fig.2 can be changed with a tabel with only the EDS analysis, the spectra can be omittted
4) For me is not clear the role of carbon showed in XPS analysis. Probably its only contaminationa and in this case the high resolution spectra of C can be omitted
Author Response
The present work involve the study of the influence of different compunds on the corrosion resistance of PEO coatings. The work is interesting and quite new but there are a lot of issues that have to be resolved before publication.
1) The main issue is the quality of the presentation and the English. The article is in a lot of parts difficult to understand (for example lines 178-196, 230-239 (paragraphs 3.3.1-3.3.3, 252-256 and also other). Morehover also the structure of the work is unclear there are too much subparagraph and is very difficult to understand the logic of the work. I suggest to revise the structure condensing some parts.
Answer: Thank you for the comment. We accept your advice and the manuscript has been thoroughly revised by the authors.
In order to condense the work, the original paragraphs 3.3.1-3.3.3 have been deleted.
2) I suggest a bit more bibliographic research oin biocompatible and antibacterial PEO coatings (see for example the works Cerchier P, Pezzato L, Brunelli K, Dolcet P, Bartolozzi A, Bertani R, Dabalà M Antibacterial effect of PEO coating with silver on AA7075, Mater Sci Eng C Mater Biol Appl. 2017 75:554-564, Mohedano M, Guzman R, Arrabal R, López Lacomba JL, Matykina E. Bioactive plasma electrolytic oxidation coatings--the role of the composition, microstructure, and electrochemical stability J Biomed Mater Res B Appl Biomater. 2013 Nov;101(8):1524-37)
Thank you for the comment. We accept your advice and the papers have been added.
3) Fig.2 can be changed with a tabel with only the EDS analysis, the spectra can be omitted.
Thank you for the comment. We accept your advice and the original Fig.2 has been displaced by Table 2.
4) For me is not clear the role of carbon showed in XPS analysis. Probably its only contaminationa and in this case the high resolution spectra of C can be omitted
In the work, all energy values were corrected according to the adventitious C 1s set at 284.6 eV. According to our results, except the adventitious C, the C peak at 286.5 eV assigned to C-O was present, which may be the product from the used carbon-containing electrolytes. Therefore, we think that in this case we had better keep the high resolution C spectrum.
Reviewer 3 Report
Plasma electrolytic treatment of magnesium alloys in fluorine-containing solutions, as the authors point out, is not a new process. However, the study of the corrosion resistance of these coatings in electrolytes with the combination of components used by the authors has a certain novelty.
However, there are several points that need to be explained or corrected.
1. Introduction (line 62), conclusion (line 440)
The authors claim based only on one source (Y. Ma et al.) that the processing time is the determining parameter of the thickness of the resulting coating in MAO process and as a consequence – the corrosion resistance of the coating. It is not so obvious. In the article of Y. Ma does not indicate the used ranges of current densities and the treatment time as well as “It was found that treatment time had significant effect on the thickness, and the KOH concentration was the most critical factor in affecting the corrosion resistance.
I believe that this part should be described in more detail.
2. Paragraphs 3.3.1-3.3.3
This material is excess in the article. The article aims to study the corrosion resistance of the sample after MAO and there is no point in describing the effect on magnesium alloy of solutions containing the studied additives. This topic may be material for a separate article.
3. Paragraph 3.4
The description of the samples used in the corrosion tests does not correspond to the composition of the MAO electrolytes (Table 1). It is should be explained or corrected.
4. Lines 451 – 469
This is a guide for authors not removed from the article.
5. Conclusion (line 445)
The authors note that changing the concentration of electrolyte components changes the content of P, F, and Zr in the coating. It is should be explained in more detail.
Author Response
Plasma electrolytic treatment of magnesium alloys in fluorine-containing solutions, as the authors point out, is not a new process. However, the study of the corrosion resistance of these coatings in electrolytes with the combination of components used by the authors has a certain novelty.
However, there are several points that need to be explained or corrected.
1. Introduction (line 62), conclusion (line 440)
The authors claim based only on one source (Y. Ma et al.) that the processing time is the determining parameter of the thickness of the resulting coating in MAO process and as a consequence – the corrosion resistance of the coating. It is not so obvious. In the article of Y. Ma does not indicate the used ranges of current densities and the treatment time as well as “It was found that treatment time had significant effect on the thickness, and the KOH concentration was the most critical factor in affecting the corrosion resistance.
I believe that this part should be described in more detail.
We highly appreciate your carefulness, conscientious, and the broad knowledge on the relevant research fields. We agree that the corrosion resistance of MAO coatings is synergistically determined by coating characteristics such as coating thickness, surface morphology and phase structure. As shown in Fig.7, except NO.4 and NO.5, the coating thickness exhibited negative effects on Icorr values of the MAO treated alloy, indicating that the coating thickness plays a main role on coating corrosion resistance. However, sample NO.7 achieved the worst corrosion resistance yet its coating thickness was not the thinnest (Table 3), indicating that besides coating thickness, other factors, such as chemical compositions and surface morphology of MAO coatings, can also influence the coating corrosion resistance. Therefore, the corrosion resistance of MAO coatings is synergistically determined and the coating thickness plays a main but not a determined role on coating corrosion resistance. We accept your advice and the manuscript has been revised.
(1) Introduction (line 62)
The original:
Treatment time is a key processing parameter, through which the coating thickness and the resulting corrosion resistance of MAO treated samples can be altered [33].
Changing into:
Treatment time is a major processing parameter and has significant effect on the thickness [36].
(2) conclusion (line 440)
The original:
The corrosion resistance of MAO coatings is synergistically determined by coating characteristics, though the coating thickness plays a main role.
Changing into:
The corrosion resistance of MAO coatings is synergistically determined by coating characteristics such as coating thickness, surface morphology and phase structure, though the coating thickness plays a main role.
2. Paragraphs 3.3.1-3.3.3
This material is excess in the article. The article aims to study the corrosion resistance of the sample after MAO and there is no point in describing the effect on magnesium alloy of solutions containing the studied additives. This topic may be material for a separate article.
Thank you for the comment. We accept your advice and the original paragraphs 3.3.1-3.3.3 have been deleted in order to condense the work.
3. Paragraph 3.4
The description of the samples used in the corrosion tests does not correspond to the composition of the MAO electrolytes (Table 1). It is should be explained or corrected.
Thank you for the comment. The measured solutions in Paragraph 3.4 may contain one, two, or three electrolytes, which is different from those in Table 1. These differences were not clearly written in the original manuscript. In the revised manuscript, we have further explained the differences.
The original:
As shown in Figure 1a, MAO coating was developed on AZ31B sample in NO.1 process, which was composed of 4 g/L NH4HF2, 8 g/L Na12Phy and 5 g/L K2ZrF6 with treatment time 2.5 min. In order to clarify the influences of NH4HF2, Na12Phy and K2ZrF6 on coating development, surface morphologies of the MAO treated samples fabricated in solutions composed of one or two electrolytes and the measured Icorr values in corresponding solutions were shown in Figure 12.
Changing into:
As shown in Figure 1a, MAO coating developed on NO.1 was fabricated in the solution composed of 4 g/L NH4HF2, 8 g/L Na12Phy and 5 g/L K2ZrF6 with treatment time 2.5 min. In order to clarify the influences of NH4HF2, Na12Phy and K2ZrF6 on coating development, surface morphologies of the MAO treated samples fabricated in solutions composed of one, two or three electrolyte solutions and the Icorr values of untreated AZ31B alloy measured in corresponding solutions were shown in Figure 8.
4. Lines 451 – 469
This is a guide for authors not removed from the article.
Thank you for the comment. The original lines 451-469 have been supplemented.
5. Conclusion (line 445)
The authors note that changing the concentration of electrolyte components changes the content of P, F, and Zr in the coating. It is should be explained in more detail.
Thank you for the comment and the part has been explained in more detail.
The original:
P, F and Zr compete with each other to enter into anodic coatings. With the increase of Na12Phy or the decrease of K2ZrF6 concentration, the P amount of anodic coatings increases. The F amount can be controlled by increasing Na12Phy concentration, decreasing NH4HF2 concentration, prolonging treatment time or increasing K2ZrF6 concentration, while the Zr content can be increased by increasing K2ZrF6 concentration, decreasing NH4HF2 and Na12Phy concentrations, or with proper treatment time.
Changing into:
· P, F and Zr compete with each other to enter into anodic coatings. The influencing rank on P content is Na12Phy concentration > K2ZrF6 concentration> treatment time > NH4HF2 concentration. With the increase of Na12Phy or the decrease of K2ZrF6 concentration, the P amount of anodic coatings increases. The sequence of processing factors on F content is Na12Phy concentration > NH4HF2 concentration > treatment time > K2ZrF6 concentration. The F amount decreases with the increasing Na12Phy concentration, decreasing NH4HF2 concentration, prolonging treatment time or increasing K2ZrF6 concentration. The order on the Zr amount is K2ZrF6 concentration > NH4HF2 concentration > Na12Phy concentration > treatment time. The Zr content can be increased by increasing K2ZrF6 concentration, decreasing NH4HF2 and Na12Phy concentrations, or with proper treatment time.
Round 2
Reviewer 2 Report
Considering that the authors have answered ti the main issues the paper can be accepted for publication
Reviewer 3 Report
Dear authors,
I believe that the corrections made in the manuscript correspond to the advices.
The manuscript can be accept in present form.
May be the conclusions can be improved.
Best regards
