Understanding Corrosion Morphology of Duplex Stainless Steel Wire in Chloride Electrolyte
Round 1
Reviewer 1 Report
Review of manuscript cmd-1264419
Understanding Corrosion Morphology of Duplex Stainless Steel Wire in Chloride Electrolyte
This paper reports on the corrosion morphology of duplex stainless steel wire in different chloride containing solutions after being polarised at 900 mV. The morphology of the lacy pits that developed was investigated.
I don’t quite understand why the corrosion was developed at the held potential of 900 mV and in solutions of pH 3. Other than ensuring that lacy pits were developed, this is in no way representative of a natural situation. The authors state in the introduction that “…the motivation of the reported work was to provide a clearer explanation of how duplex stainless steels corrode in chloride-containing solutions, which form the majority of most engineering applications”. Being polarised at 900 mV, at pH 3 and 60 °C is not the majority of engineering applications. The authors need to clearly state why these conditions were chosen. If it was to guarantee lacy pit formation in order to study these types of morphologies then that is fine, but state that!
The only other comment I have is there are some strange phrases used without the paper, such as “occluded nasty electrochemistry”, “environment is here decisive as active”, and “electrochemistry is harsh”. I suggest the authors reconsider rewording these sentences.
Author Response
Thank you for your comments. Please find the attached word document to see our response, and also see the revised manuscript.
Author Response File: 
Author Response.docx
Reviewer 2 Report
paper is well presented and the conclusions are consistent with the results. the graphic material is adequate
Author Response
Thank you for the positive feedback! Highly appreciated!
Reviewer 3 Report
Interesting and well written paper that can be published as it is.
Author Response
Thank you for the positive feedback! Highly appreciated!
Reviewer 4 Report
The structure of the introduction is:
- text,
- aim declaration 1: ‘The corrosion morphology in duplex stainless steel has not been thoroughly explained. Therefore, the motivation of the reported work was to provide a clearer explanation of how duplex stainless steel corrode in chloride-containing solutions, which form the majority of most engineering applications’,
- text,
- aim declaration 2: ‘The work reported in this paper discusses the corrosion forms of duplex stainless steel in chloride-containing aqueous electrolyte and shows that pitting corrosion of duplex stainless steel occurs by deterministic and probabilistic grounds depending on the chloride ion concentration. Particular focus is given to the nature of pit cover formation to understand the effect of microstructure. Stress is also given to the possible reasons for the destruction of the lacy pit cover. The aim is to foster an understanding of the corrosion mechanism of duplex stainless steel.’
- I suggest to develop the test in a whole treatment, and, declaring the aim at the end of the introduction integrating aim declarations 1 and 2.
- as mentioned in ‘aim declaration 1’ a clearer explaination is wellcome about the linkage between your work and to majority of the most engineering applictions, since the only variable you explore is [NaCl] (pH and T are fixed at 3 and 60°C): are these pH/T conditions tipical of any particular application? Or, is your investigation rather a kind of accelerated test pushing pH/T ? In pag.5 you said ‘Grade 2205 duplex stainless steel is immune to pitting at room temperature and only suffers from pitting corrosion above the critical pitting temperature which is 40°C [50]..’
- Did you perform tests in control conditions (T-room, neutral pH) ?
On my opinion, this aspect is important to be explained.
About the section ‘corrsion morphology’, I suggesto to describe the phenomena following the 0.01, 0.1 and 1 M order, i.e., referring 0.1 and 1 observations to 0.01 M scenario. In general, the discussion might follow this logic.
The paragraph starting with ‘Figure 5a shows a corrosion pit (developed in 1 M solution) with a lacy cover having collapsed partially..’ (pag.8), on my opinion deserves a title as ‘cover collapse and hydrogen embrittlement’, or similar. This would help the reader..
Author Response
Thank you for your valuable comments. Please see the attached word document to see our response to your comments, and also see the revised manuscript.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Thank you for addressing all the reviewer comments/concerns. I am happy that this paper is now in a fit state for publishing.
Author Response
You are welcome. We also thank you for your valuable time in providing constructive feedback to our paper.
Reviewer 4 Report
A) on question
[1] Did you perform tests in control conditions (T-room, neutral pH) ? On my opinion, this aspect is important to be explained.
you clarified
Yes, we carried out many experiments at different temperatures, pH, chloride concentration, static potentials, heat treatment, and surface finish. In this paper, we want to provide a mechanistic description of the corrosion morphology in chloride-containing solution and not describe the pitting behaviour as a function of temperature or pH. There are numerous publications for the latter two.
Consider to give this information in the paper too.
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B)
[1] About the section ‘corrsion morphology’, I suggesto to describe the phenomena following the 0.01, 0.1 and 1 M order, i.e., referring 0.1 and 1 observations to 0.01 M scenario. In general, the discussion might follow this logic.
Thank you but we believe that either way is okay. No changed made.
My opinion, as reader, is on a more helpful 0.01, 0.1, 1 M order, but, of course, I respect your opinion as well as Editor's one.
Author Response
Thank you again for your valuable time and constructive criticism of our work. Comment A has been addressed as follows at lines 164-171 in the revised manuscript (version R2):
"It should be noted that we performed many experiments at different temperatures, pH, chloride concentration, static potentials, heat treatment, and surface finish; however, the aim of this research is to provide a mechanistic description of the corrosion morphology in chloride-containing solution only and not to describe the pitting behaviour as a function of environmental conditions. The reader is referred to other publications for understanding the pitting behaviour as a function of temperature [29, 46-49], pH [32, 50, 51] or other environmental parameters [10, 13, 28, 52-56]. After the corrosion experiments, [...]"
