Corrosion Mechanism of L360 Pipeline Steel Coated with S8 in CO2-Cl− System at Different pH Values
Round 1
Reviewer 1 Report
Dear authors,
I enjoyed reading the manuscript because the paper is well-described, and the results are clearly demonstrated. The authors have made a good synthesis of the literature that provides an overview of the research evolution in this area.
This manuscript, entitled „ Corrosion Mechanism of L360 Pipeline Steel Coated with Elemental Sulfur in 3.5 wt% NaCl Solution Containing CO2 at Different pH” is relevant to the scope of this journal. It is an interesting study that can provide interesting information to specialists.
Before being published, I recommend that the authors make a small correction: the legend of Figure 8 should specify the pH for each case.
Author Response
Dear Editors and Reviewers:
Thank you for your letter and the referee’s evaluation and comments on our paper “Corrosion mechanism of L360 pipeline steel coated with elemental sulfur in 3.5 wt% NaCl solution containing CO2 at different pH” (ID: metals-1467454). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have revised the manuscript according to your kind advices and the referee’s detailed suggestions. Here we attached the revised manuscript in the formats of MS Word, the responses to the reviewer’s comments are also enclosed, and the revised parts are marked in red in the paper.
Best regards
Sincerely yours
Jinling Li
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Corrosion mechanisms of L360 Pipeline Steel coated with elemental Sulphur in 3.5 % NaCl solution containing CO2 at different pH
The paper deals with electrochemical study including Wire beam electrode current distribution, surface characterization of steel and steel covered with Sulphur in 3.5 % NaCl solution at different pH values. The paper is well structured and the topic is well presented. However some changes are necessary in order to improve the scientific quality of the paper.
The optimum title character count is 85
Abstract: ok
Keywords: ok
Introduction: Ok, but, the gap sentence is missing. What is the novelty of this particular paper, what has not been studied yet and which questions remain open?
Materials and methods
2.1 Solution
pH was controlled by NaOH and H2SO4? Why? Could sulphate ions react as inhibitors? How much (in M) SO42- was added in the case of pH 3.10 and 5.15?
Why were this pH values chosen?
2.3
Electrode preparation
Of 2r diameter of the wire is 1.5 , then the area of exposed electrodes is 1.766 cm2 and not 1.72 cm2. Which value is correct?
2.4 Frequency range of EIS measurement is 10 kHz down to 10 mHz.
The sxan rate was 0.3 mV/s and not (0.3 mv/s and the potential was 500 mV and not 500 mv vs OCP.
Why did you chose 60 °C as the operating temperature? How did you conduct experiments at 60 °C. If SCE electrode was used at 60 °C, what was the potential at 60 °C. Did you verify the operating temperature of SCE electrode?
Results
3.1 Potentiodynamic polarization curves
In the text and figures systematically present first bare and then S8 coated samples or the other way around, since it is difficult to follow if Tables , text and Figures have different way of order.
Figure 1:
In order to see clearly: potential scale should be similar in both figures, also current- much better way of presenting is the logarithmic scale and not logarithmic values.
Figure caption: state solution (3.5% NaCl with different pH), T and scan rate. Also- the term electrode could be more specific: steel.
Size of graph: should be bigger, also size of fonts and numbers
Table 1: It is not acceptable to show values with so many decimal points.
Three significant numbers is acceptable for electrochemical parameters.
About results:
“As shown in Fig 1a, the anode was active.” Did authors wanted to say that the potentiodynamic scans in anodic region point at active dissolution?
The anode Tafel slope is not correct term! How do authors recognize diffusion controlled process in cathodic region forS8 coated steel?
Self- corrosion potential is not common term in electrochemistry? Ecorr or corrosion potentials ok and it is _610 mV and not -610.678MV.
Also, instead writing mV vs SCE in Figures etc, simply insert a sentence in Experimental description that Potential values in manuscript are defined against SCE unless otherwise stated.
Also, is corrosion current density really so high, around 0.6 mA/cm2?
EIS
Similar as for potentiodynamic results: If graphs are presented bare first and then S8 coated steel, also Table should be similar.
Qdl: if presented number×10-3 then (mF cm-2) is not suitable way of presenting it.
Again- the decimal numbers not needed.
The sentence: ”Different circuits were used to simplify…” should be rewritten since not the common EIS terms are used.
Equivalent circuits are used in order to find physical meaning to the observed electrochemical process (and not mechanical).
State: quality of fitting (chi square) and range of fitting (high frequencies omitted).
3.3 Potential and current distribution:
All graphs and figures as well as figure captions should be on one page in order to have clear presentation. Numbers on graphs are barely visible. Not possible to distinguish when printed.
Potential and current graphs at certain pH should be plotted together in one line in order to observe the results.
When you describe results, always state observation and for which material (steel, S8 coated, and pH), otherwise it is difficult to follow.
Figure caption number of anodes: NA would be better than Na (sodium)
3.4 Surface and component characterization
Component characterization is not understandable, what is that.
Figure 8: state, which electrode was observed (6/6), was it the one with more anodic or more cathodic nature? Explain
Corrosion mechanism
What is the proof that cathodic reaction (S) is reduction of carbonic (VI) acid?
References: A list of 30 references is used in the paper. DOI numbers are missing.
Author Response
Dear Editors and Reviewers:
Thank you for your letter and the referee’s evaluation and comments on our paper “Corrosion mechanism of L360 pipeline steel coated with elemental sulfur in 3.5 wt% NaCl solution containing CO2 at different pH” (ID: metals-1467454). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have revised the manuscript according to your kind advices and the referee’s detailed suggestions. Here we attached the revised manuscript in the formats of MS Word, the responses to the reviewer’s comments are also enclosed, and the revised parts are marked in red in the paper.
Best regards
Sincerely yours
Jinling Li
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have improved the quality of the paper. I have no more objections.
Author Response
Dear Reviewers,
Thank you for reading our article carefully and guiding my article. Your opinion plays a great role in improving the quality of my article.
Best regards,
Sincerely yours
Jinling Li
Author Response File: Author Response.pdf
