Use of Time Domain Nuclear Magnetic Resonance Relaxometry to Monitor the Effect of Magnetic Field on the Copper Corrosion Rate in Real Time
, Bruna Ferreira Gomes 2,*, Elaine Paris 3, Carlos Manuel Silva Lobo 4, Christina Roth 2 and Luiz Alberto Colnago 3Round 1
Reviewer 1 Report
The manuscript deals with an interesting approach in copper corrosion studies under magnetic field. The manuscript is interesting but some issues need to be addressed with more caution in order to support the main conclusions.
As the main topic of the paper is copper dissolution in 1M HCl it is strongly recommended to examine and cite more than just one paper dealing with this topic. There was a lot of work conducted at the end of the last century. Many of these papers show that in the solutions containing significant amount of Cl-, copper oxidation goes through formation of CuCl complex which then dissolves as CuCl2- while only small amount of Cu2+ is formed (see for examples D.Tromans, R.Sun, J.Electrochem.Soc. (138)1991, 3235). Thus it is not clear if Cu2+ concentration is good indicator of copper corrosion rate. Please comment on that. In my opinion such approach would be more appropriate for H2SO4 solutions where dissolution into Cu2+ is expected.
AFM shows that for B>0 surface becomes much rougher than for B=0. Roughness of the surface in principle increases with the dissolution rate, especially in such aggressive solutions like 1M HCl. In this manuscript the opposite conclusion was drawn!
How many areas of the same sample were examined by AFM? Just one, or was measurement conducted at several spots?
Figure 6- what is meant by ex-situ and in-situ XRD? In-situ like in magnetic field or in 1MHCl?
As the Cu dissolution in HCl results in CuCl formation how do you explain that no CuCl was observed for samples B=0? Was it maybe washed out due to rinsing? My concern is that these results lead to the opposite conclusion from one given in the paper, that high dissolution rate of Cu in B>0 resulted in formation of thick layer of CuCl and roughening of the sample. On the other hand in B=0 Cu dissolution rate might be lower resulting in negligible CuCl formation which then easily dissolves and is not clearly observed by XRD. The manuscript proposes that CuCl acts as passivating layer, but if you examine relevant corrosion literature you will find that easily soluble compounds like CuCl cannot be considered as passivating phase, as passivity is related to corrosion products with extremely low solubility.
I believe that some additional method (electrochemical, gravimetric) would be helpful to actually confirm your conclusions.
Conclusions: „The accumulation of more Cu2+ ions in the vicinity of the electrode surface hinders the arrival of the corrosive agent, maintaining the passivating CuCl phase for a longer time.” If Cu2+ is accumulating near the Cu electrode surface wouldn't that result in attraction of the opposite charged ions, like Cl- and their increased mobility towards Cu surface? Maybe the high Cl- concentration close to surface is a reason why lot of CuCl is formed?
Author Response
We thank the reviewer for all the suggestions and comments. We addressed all the comments one by one in the attached document.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Review for
magnetochemistry-1626335
Use of time-domain nuclear magnetic resonance relaxometry to monitor the effect of magnetic field on the copper corrosion rate in real time
The effect of magnetic fields on copper corrosion has been addressed by many researchers. This topic is significant and should pay much attention to it. I think, nonetheless, that the manuscript could be improved if the authors could address the comments and recommendations I listed below.
Numerous similar works have been published, please state your novelty. Additionally, the novelty of this article should be highlighted in the Abstract.
The practical application background of your research should be covered in the Intro.
Will you be about to give a specific number of B( ? T).
AFM analysis is important which gives 3-D morphology information. However, SEM observation is also important. If possible, an SEM morphology analysis with EDS is highly recommended.
In figure 4. Please add a label to the figure. What is the black dots stand for and what is the red dots stand for.
Line 188: I did not find Equation 11 in your article.
Your corrosion tests only rely on AA measurements, which lack convincing. At least, you should add a potentiodynamic polarization test to determine the corrosion rate of copper.
Your research lacks cyclic voltammograms(CV) tests. CV is pretty basic and significant for the study of Cu corrosion.
If possible, XPS is highly recommended. The oxidation state of many corrosion products is an important factor for your mechanism analysis.
Author Response
We thank the reviewer for all the suggestions and comments. We addressed all the comments one by one in the attached document.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have explained all questionable issues and the manuscript is acceptable for publication.
Reviewer 2 Report
After checking the draft of the response to the comments, and the corresponding revisions in the revised manuscript, I found that the authors have accomplished the recommended revision to address all my concerns.
As a consequence, this manuscript can be considered for publication.
