The Cu Ions Releasing Behavior of Cu-Ti Pseudo Alloy Antifouling Anode Deposited by Cold Spray in Marine Environment
, Yuhao Wang 3,4, Shuai Wu 1, Hongren Wang 3, Jiancai Qian 1, Li Ma 3 and Guosheng Huang 3,*
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsAuthors should try not to use abbreviations in the abstract.
The figures and their descriptions need improvement.
- Fig. 1a) The description is not precise enough; it should be “macro galvanic corrosion” because currently the descriptions of Fig. 1a) and 3a) are identical.
- Fig. 1b) The photos are too small.
- Fig. 3a) the description is not precise enough, it should be “micro galvanic corrosion”.
- Fig. 3 missing description of parts a) and b), similarly Fig. 4 a)-g)
- Fig. 3a) what does the Chinese inscription in the figure mean?
- line 93, Fig. 3a) or Fig. 3b)?
The authors should correct the numbering of the equations. And so, in line 166 Equotion (1), is it Eq 1 from line 11 or from line 185?
- line 199 Equotion() and Equotion() ???
The paper also requires some technical and linguistic corrections, such as missing spaces before words and capital letters in the middle of sentences. There are a few such errors, e.g., lines 223, 352, 415.
“In witch:” after equations with a capital letter - perhaps better where: (written with a lowercase letter).
In conclusions, the authors state that they performed SEM, EDS, and XRD analyses. Similar information can be found in Chapter 2, Experiments and Methods. Therefore, my question is: where are the XRD test results?
Author Response
Detail response is enclosed in the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors investigate the Cu(I/II) releasing behavior of a Cu–Ti pseudo-alloy antifouling anode deposited by cold spray for marine applications. The study aims to evaluate ion release kinetics, microstructural characteristics, and electrochemical stability of the coating in seawater environments. Through morphological, compositional, and electrochemical analyses, the authors attempt to correlate coating structure with copper ion release efficiency and antifouling performance. The topic is relevant and promising for the development of environmentally friendly antifouling materials; however, the manuscript would benefit from additional clarification, data refinement, and deeper discussion to strengthen its scientific contribution.
Major Comments, Questions, and Suggestions:
- Clarify the novelty and objectives by explicitly stating how the Cu–Ti pseudo-alloy differs from conventional Cu- or Cu–Ni-based antifouling systems, and what specific advantages are expected from titanium addition.
- Provide detailed experimental information on the cold spray deposition parameters such as gas type, pressure, temperature, particle velocity, and standoff distance, as these directly affect coating density and adhesion.
- Expand the microstructural characterization by presenting quantitative data from SEM/EDS or XRD, including grain size, phase composition, and Ti distribution within the Cu matrix.
- Include detailed results on Cu⁺/Cu²⁺ concentration as a function of immersion time and explain clearly the analytical method used for ion quantification (e.g., ICP-OES or UV–Vis).
- Discuss the electrochemical data more thoroughly, emphasizing the link between potential evolution, corrosion rate, and ion release behavior, and comparing results with existing literature.
- Improve the figures and tables by enhancing resolution, ensuring consistent units and labeling, and clarifying captions to better highlight trends and key findings.
- Strengthen the conclusion by summarizing the main quantitative results, emphasizing structure–property–performance relationships, and suggesting future work on optimizing Cu/Ti ratios, coating thickness, or long-term antifouling durability in real marine conditions.
Author Response
Dear Editor and reviewers:
We are very glad to receive your letter. Thank you for your letter and reviewers’ valuable comments concerning on our manuscript ID coatings-3938938 entitled " The Cu ions Releasing Behavior of Cu-Ti Pseudo Alloy Antifouling Anode Deposited by Cold Spray in Marine Environment ". The comments are valuable for improving our paper, which is also helpful for guiding our future works. And we studied the comments carefully. At the same time, we checked the paper carefully according to the comments and made corresponding revisions. Finally, the point-to-point responses to the criticisms are listed as follows and revised version is re-uploaded through submission system. All revised parts in the manuscript are highlighted with red color.
Answer to reviewers' comments (2):
The authors investigate the Cu(I/II) releasing behavior of a Cu–Ti pseudo-alloy antifouling anode deposited by cold spray for marine applications. The study aims to evaluate ion release kinetics, microstructural characteristics, and electrochemical stability of the coating in seawater environments. Through morphological, compositional, and electrochemical analyses, the authors attempt to correlate coating structure with copper ion release efficiency and antifouling performance. The topic is relevant and promising for the development of environmentally friendly antifouling materials; however, the manuscript would benefit from additional clarification, data refinement, and deeper discussion to strengthen its scientific contribution.
Major Comments, Questions, and Suggestions:
- Clarify the novelty and objectives by explicitly stating how the Cu–Ti pseudo-alloy differs from conventional Cu- or Cu–Ni-based antifouling systems, and what specific advantages are expected from titanium addition.
Responds: The corrosion rate of Cu alloy with Ni, Zinc and aluminum is usually lower than pure copper (TUP), since the formation of the passivation film on the surface of the alloy in seawater. The corrosion rate decreases as the immersion time increases. While for the Cu-Ti pseudo-alloy, the Cu can be polarized by the Ti, which could be found in the introduction part as shown in the figure below. The corrosion rate increases tens times as the potential is polarized 100 mV positively, which could enhance the antifouling performance of the copper alloy. As we known from the engineering and literature, Cu-Ni alloy is the most anticorrosion copper alloy, which has the poorest antifouling performance. So we worry whether Ti can accelerate the corrosion of Cu or not.
This is the first time to use corrosion phenomenon to get positive effect.
Figure 1 The accelerating effect of Ti additional in Cu alloy
- Provide detailed experimental information on the cold spray deposition parameters such as gas type, pressure, temperature, particle velocity, and standoff distance, as these directly affect coating density and adhesion.
Responds: These parameters are listed in Table 3 in the text.
The velocity for different type of particles and different diameter particles are different, and to know the particles’ velocity needs LDP monitoring method or Fluent CFD software simulation method, which is beyond the research scope of this work.
Table 3. CS parameters for depositing Cu-Ti anode.
|
Temperature (℃) |
900．0 |
|
Pressure (MPa) |
5.5 |
|
Temperature (℃) |
750 |
|
Stand-off distance (mm) |
25.0 |
|
Process gas |
N2 |
|
Powder feeding rate/(g·min-1) |
40.0 |
- Expand the microstructural characterization by presenting quantitative data from SEM/EDS or XRD, including grain size, phase composition, and Ti distribution within the Cu matrix.
Responds: Figure 15 show the SEM photograph of the anode, which includes the particles shape and size in the anode. The galvanic corrosion is mainly influenced by the material type and the portion, so in this work, the detail composite and phases were not investigated.
The detail data of SEM/EDS were included in the previous work (GU Songlun ZHANG Fan, HUANG Guosheng, JIANG Dan, DONG Guojun. Corrosion Behavior of Cold Spray Cu-Ti Pseudo Alloy as Anti-fouling Material in Natural Seawater[J], Journal of Chinese Society for Corrosion and Protection, Vol.45 No.5 Oct. 2025, pp: 1310-1321, DOI 10.11902/1005.4537.2024.347).
The Ti distribution within the Cu matrix were discussed in the text, the volume fraction is consistence with the powders.
- Include detailed results on Cu⁺/Cu²⁺ concentration as a function of immersion time and explain clearly the analytical method used for ion quantification (e.g., ICP-OES or UV–Vis).
Responds: The method can be found in previous paper “GU Songlun ZHANG Fan, HUANG Guosheng, JIANG Dan, DONG Guojun. Corrosion Behavior of Cold Spray Cu-Ti Pseudo Alloy as Anti-fouling Material in Natural Seawater, Journal of Chinese Society for Corrosion and Protection, 2025, 45(5), pp: 1310-1321, DOI 10.11902/1005.4537.2024.347”, which could be found in the figure below (a series standard concentration Cu ion samples was measured, and a calibrated line was drawn, then the test sample was measured to find the concentration on the line):
How was the Cu(I/II) concentration measured
- Discuss the electrochemical data more thoroughly, emphasizing the link between potential evolution, corrosion rate, and ion release behavior, and comparing results with existing literature.
Responds: literature was added to discuss the potential evolution, corrosion rate, and ion release behavior.
- Improve the figures and tables by enhancing resolution, ensuring consistent units and labeling, and clarifying captions to better highlight trends and key findings.
Responds: figures and tables are improved by adjusting the size and resolution.
- Strengthen the conclusion by summarizing the main quantitative results, emphasizing structure–property–performance relationships, and suggesting future work on optimizing Cu/Ti ratios, coating thickness, or long-term antifouling durability in real marine conditions.
Responds: There are some engineering concerns on this kind of anode, in this paper the applicable of this kind of anode is verified. Next step, we will construct some more noble cathodic phase to enhance the potential difference between cathode and anode since the pipeline needs very high Cu ion concentration. We will do further investigation on this topic by taking passivation film into consideration in the future.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsSummary: In this paper a cold spray coating pseudo-alloy of copper and titanium is characterised for its ability to preferentially corrode for anti-fouling applications in high velocity seawater. COMSOL modelling and some real corrosion studies are used to analyse the materials.
General comments:
Can the authors please undertake a review of the grammar of this manuscript? There are numerous instances of incorrect absence of the plural form of a word as well as other issues. E.g. “Coatings with anti-fouling agent”, agent should be pluralised to agents.
Specific comments:
When the authors say that coatings are not applicable for anti-fouling in high velocity seawater, is it that coatings are typically not used in this environment? Is it literally the deposition that is an issue? Delamination of the coating? There are certainly coatings that could be applied to provide benefit but I’m curious as to why not applicable is the phrase used.
As the authors have found that varying the wt.% of Ti can vary the ion release, is there any mileage in optimising this for different environments? What are the next steps to further enhance this work?
Line 53 “Electrochlorination can produce hypochlorous acid, The first one is an active one by applying a potential or imposing a current to an MMO (mixed metal oxides) or noble metal (Pt) electrode placed at the vicinity of the material to be protected or to the material surface itself.” Please can the authors review this sentence? The clauses do not make sense.
Line 98: Are there any other potential environmental concerns with this methodology?
Line 116: Kill the biology? Can the authors please refine this phrasing.
Line 147-155: Can the authors rework this part please? It reads like a COMSOL advertisement.
Line 159: Is seawater available as an element in COMSOL? Does it have standardised properties?
Figure 4: Please explain the subfigures in the figure caption.
Line 177: Did the authors just automatically use the mesh option in COMSOL? Was there any mesh optimisation study carried out? I think this is especially important due to the inclusion of the ε parameters which involves mesh size in the domain.
Line 245: Was it an immediate change from 200 grit to 600 grit? What was the load applied?
What potentiostat was used for this testing?
Table 1 and 2: There appears to be a formatting error with these tables. Should the symbols not be used? It appears to be incorrectly formatted LaTeX code.
Line 270: What is the mean size of both particles?
Table 3: Can the authors please check the formatting of this table?
What was the coating deposition time and resultant thickness?
Line 277: What was the load applied and any rotational parameters (if using an auto-polisher)?
Figure 9: Can the authors please improve the labelling and add scale bars to these figures? Can this also be applied to other similar figures?
Figure 10: Please provide more details in the caption to make it clear what the subfigures represent.
Figure 11: What are the yellow circles? There is no indication or description for these in the text or captions.
Line 356-357: Why do the authors suppose this to be?
Figure 14: Is there a subfigure missing?
Lack of references and discussion. Can the authors please improve on this aspect to compare, contrast and explain the results with other published works?
Line 391: Excellent bonding character, can this be quantified?
Line 407: incomplete sentence?
Figure 15: Why are the sub figures labelled as they are? Yellow box annotation?
I believe the authors can do more to relate the modelling work to the real corrosion results. Currently they sit as two separate sections of the paper but should the related and synthesised together.
Comments on the Quality of English LanguageA full grammatical review is required for incorrect pluralisation and general phrasing. There are also incomplete sentences that need revision.
Author Response
detail answer can be found in the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsFig. 11 is not visible.
Fig. 15 The markings in the figure are c) and a).
Information on XRD measurements is still included in the conclusions.
The correct order of first and last names in Author contribution has not been preserved.
Added reference 34 has been written in a different style.
Author Response
The responses are in the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have addressed all reviewer feedback, thereby enhancing the clarity and overall quality of the paper. The manuscript is now suitable for publication in the journal Coatings.
Author Response
The responses are in the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsI thank the authors for their thorough review of the manuscript. There still appears to several formatting issues to address:
Please can the authors check the formatting of equation 11? Micro does not look correct here.
Table 2 still requires revision. The same issue is still present.
Fig 11 appears to just be a yellow box. Can the authors please check this?
Author Response
The responses are in the attachment.
Author Response File: Author Response.pdf
