Effect of CO2/H2S and Applied Stress on Corrosion Behavior of 15Cr Tubing in Oil Field Environment
Round 1
Reviewer 1 Report
- Authors should check subscripts or exponents throughout the document.
- What is "a corrosion rate in mm/a"?
- Why did the authors choose a stress value equal to 80% yield strength?
- The figures presenting the EDS results are not clear enough.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This manuscript deals with the influence of CO2/H2S and applied stress on behaviors of corrosion and stress corrosion. I think that this study is interesting and valuable to engineers, but I have some concerns about the manuscript and experimental technique. The manuscript probably deserves to be published after a major revision.
- This manuscript would benefit tremendously from language editing by either a native English speaker or a professional editor. There are a large number of grammatical and typographical errors throughout the manuscript.
- Please explain experimental techniques, especially bend testing. I cannot understand how to determine applied stress using eq. 2. The values of E and y are not explained in this manuscript.
- I think that the mechanical properties of 15Cr steel were measured at room temperature (approximately 20 C). The mechanical properties depend on temperature. The mechanical properties at these temperatures should be explained because the experiments were conducted in 90 or 150 C.
- It is well-known that grinding and polishing induce the tensile residual stress on a specimen surface, which is several hundreds MPa. I think that this residual stress cannot be ignored. Please explain the residual stress of each specimen used in this study.
- According to Figs. 2 and 3, a lot of scratches are observed. The scratches affect the corrosion rate and cracking behavior due to the increase in surface area. Please explain the scratches and their influences.
- How many specimens did you use? I am worried about the reproducibility of the experimental results.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I think that this manuscript should be accepted in present form.
Author Response
Dear reviewers, I did not find the second revision opinion, but according to your revision opinion last time, I revised and improved the manuscript and explained it. Thank you very much!
Author Response File:
- Address English style to improve readability.
Answer: Thanks for reviewers’ comment. we have made in-depth revision of the manuscript this time, hoping to improve the readability of the manuscript. (Seen the color-marked content).
- Explicitly address reproducibility (number of replicates) in the experimental section. You shall also address test-to-test variability in the results section.
Answer: Thanks for your reminding. In order to ensure the accuracy and reproducibility of the results, there are three parallel specimens in each stress test, and the effective test is only when the specimen breaks or cracks in the working area.
Four parallel samples are taken from each group in each weight-loss test . One sample is used to observe the corrosion morphology, and the other three are used to calculate the average corrosion rate to ensure the accuracy and reproducibility of the results. Therefore, the experimental results are reliable.
Lines 77-78 and 82-84 of the manuscript: The number of parallel samples in weightless experiments is explained.
Lines 96-98 of the manuscript: The number of parallel samples in stress corrosion experiments is explained.
Line 148 of the manuscript: the author increased the deviation between parallel samples in the experiment, as shown in Table 1.
- In your response to Reviewer 1, you stated "The experimental material in this study was API tubing of 110 steel grade." this is incorrect as the study concentrates on 15Cr stainless steel. What was the product form? please indicate UNS number.
Answer: Thanks for your question. The experimental material in this study was 15Cr-6Ni-2Mo tubing, and yield strength was 110 kpsi. The samples were cut from 15Cr-6Ni-2Mo martensite stainless steel commercial tubing , it is a newly developed martensitic stainless steel tube, which has no uniform serial number at present.
Line 58 of the manuscript: The author added a description of the experimental material 15Cr-6Ni-2Mo.
- Authors should check subscripts or exponents throughout the document.
Answer: Thank you for your reminding. I have checked the subscript and index of the whole article and made changes. (Seen the color-marked content).
- What is "a corrosion rate in mm/a"?
Answer: Thank you for your question. There are many ways to express the corrosion rate. One of them is the way to express the corrosion depth. The common unit is mm/a, which means that the corrosion thinning depth of materials is calculated in years.
Line 87 of the manuscript: the author describes the unit of corrosion rate, mm/a
- Why did the authors choose a stress value equal to 80% yield strength?
Answer: Thanks for your question. In this study, The experimental material was 15Cr-6Ni-2Mo martensitic stainless steel tube with nominal yield strength of 110 kpsi. In accordance with the requirements of API 5CT standard, 110 grade of tubing load stress is 85% YSmin (758 MPa) = 644 MPa, but in the actual test, according to the requirements of the project, load stress value using the actual yield strength value of the sample (825 MPa) rather than the nominal yield strength (758 MPa), so the appropriate reduction ratio coefficient was 80%, when the stress load value is 825×80% = 660 MPa, so the stress value in line with the requirements of 85% YSmin.
Lines 104-106 of the manuscript: the author provides a detailed description of the stress applied to 80% of the actual yield strength.
- The figures presenting the EDS results are not clear enough.
Answer: Thank you for your reminding. I have provided clear values of EDS results.
Lines 216, 227 of the manuscript: the author provided clear values of EDS results.
