Tribological and Anticorrosion Performance of Electroplated Zinc Based Nanocomposite Coatings
Round 1
Reviewer 1 Report
The paper “Tribological and anticorrosion performance of electroplated zinc based nanocomposite coatings” studies the tribological and corrosion behaviour of zinc and composite zinc coatings containing hard nanoparticles. Here are my questions:
- The introduction part need to develop and use some new works.
- This puzzling paper has some interesting results and possible explanations. Is this data reproducible?
- “… It indicates that the inclusion of nanoparticles can increase corrosion resistance by delaying white rust formation.” What do authors mean by “delaying”? All of the interactions should be described.
- The novelty of the paper is not clear.
- Page 7, the sentence is unclear: “.…consisting mainly of oxygen and iron, deposited on the edges of the friction trace,.” why?!
Author Response
We would like to thank the referee for their comments, and we are pleased to improve the manuscript according to suggestions. We have provided a point-by-point response below to feedback and have modified the text and figures accordingly (shown in the manuscript in RED).
The paper “Tribological and anticorrosion performance of electroplated zinc based nanocomposite coatings” studies the tribological and corrosion behaviour of zinc and composite zinc coatings containing hard nanoparticles. Here are my questions:
The introduction part need to develop and use some new works.
Introduction part was developed, and new references were added. However, since a manuscript is a communication, the length of the introduction part cannot be excessive. Following sentences and references were added:
The nanoparticles fill voids in zinc matrix, providing barrier properties by blocking active sites for corrosion initiation [7]. In terms of enhancing mechanical properties, the nanoparticles dispersed in the coating can hinder the easy movement of dislocations, thus increasing coating’s hardness [8].
- Mohammadnejad M., Habibolahzadeh A., Yousefpour M., Effect of Nano Oxide Addition on Corrosion Performance of Hot Dip Zinc Coating, Pot Met Phys Chem, 2016, 52, 100.
- Conrad H., Golden T., Electrodeposited Zinc-Nickel Nanocomposite Coatings, Nanocomposites – Recent Evolutions, 2018, IntechOpen.
This puzzling paper has some interesting results and possible explanations. Is this data reproducible?
During the tests, three measurements were made to determine the standard deviations and assess the repeatability of the results. Reproducibility testing would require additional measurements (in other laboratories and other devices) that we did not carry out.
“… It indicates that the inclusion of nanoparticles can increase corrosion resistance by delaying white rust formation.” What do authors mean by “delaying”? All of the interactions should be described.
‘Delaying white rust formation’ means slowing down corrosion process. Composite coatings display lower amount of white rust comparing to plain zinc coatings, because nanoparticles fill the microholes at coating surface and block active sites for corrosion initiation. The manuscript was amended accordingly. Please see changes below.
Corrosion products of Zn/NP coatings are much less visible. It indicates that the inclusion of nanoparticles can slow down the corrosion process. This delaying of white rust formation is the result of enhanced barrier properties of nanocomposite coatings comparing to pure zinc coatings.
In addition, coated samples were stored for six months in a dry room at a constant temperature of 19 - 22°C. The microscopic analysis presented in Fig. 2A,C showed that Zn coatings were all covered with white rust. For Zn/NP composite coatings white rust phenomenon was much smaller and occurred locally (Fig 2B,D).
The novelty of the paper is not clear.
To the best knowledge of the authors presented paper is the first report of using confocal laser scanning microscopy (CLSM) to study the properties of the metallic coatings plated on the steel substrate. To be able fully to deploy the abilities of this technique the two types of materials – the traditional zinc-based coating, and the coating obtained the same way but with the addition of nanoparticles (composite one) were investigated. What is worth to highlight too, zinc nanocomposite coatings were obtained not from an experimental bath, but employing commercially available products.
The manuscript was amended to make its novelty clearer.
Besides traditional tribological methods, the confocal laser scanning microscopy (CLSM) was used for the first time to characterise the metallic coatings. To the best knowledge of authors, this was the first successful attempt to produce zinc nanocomposite coatings from commercially available products.
Page 7, the sentence is unclear: “.…consisting mainly of oxygen and iron, deposited on the edges of the friction trace,.” why?!
The zinc layer underwent the abrasion process quickly, thus exposing the sample core, whose main component was iron. As a result of the energy supplied during friction, iron oxidation and formation of oxide wear products took place, which were separated to the edges of the friction trace due to low adhesion to the substrate.
The unclear sentence has been rewritten. We hope that now it is more understandable. „EDS analysis has shown that wear products consisting mainly oxygen and iron were moved to the edges of friction zone.”
Reviewer 2 Report
Dear Authors,
This research study is interesting and it could be published after a minor revision. I mentioned in text some observations/corrections/suggestions as follows:
Lines 12-19: the “Abstract” must be improved, by introducing more details about the nanocomposites.
Lines 22-39: The section “Introduction” must be improved, and then the section “References” must be updated.
Line 42: Authors must specify the type of nanoparticles in “metal oxide hard nanoparticles”.
Authors must give more details about the preparation of nanoparticles: method, type etc. and they must insert a reference from scientific literature.
Authors must prove the formation of nanoparticles!
Line 46: Authors must specify the components of these Zn nanocomposites.
Line 47: Authors must specify the type of additive. Authors must also specify the correct name of “coat-it company”.
Line 132: Replace “rougnes” with "roughness".
Lines 133-135: Authors must reformulate the sentence:
“Microscopic analysis of friction marks, presented in Fig. 5 and 6, allows to conclude that as a result of sliding wear debris accumulated, which remained in the wear area, and led to intensification of second wear processes.”
Line 149: What is the difference between Figures 7A and 7B, and between Fig. 7C and 7D? Please correct the legend of Fig.7:
A, C - Zn coating;
B, D - Zn nanocomposite coating
Lines 161-162: Authors must specify the type of nanoparticles, the type of additive, and also the correct name of the company in the sentence: “Nanoparticles were introduced into coating by applying the plating additive provided by the coat-it company.”
Line 167: The word “of” must be deleted in: “to optimise of the coating composition”.
Line 168: Authors must specify the type of nanoparticles they used in this study.
Line 180-198: I observed very few references!
The authors did not demonstrate the obtaining of nanoparticles and did not specify what type of nanoparticles they used.
Authors must specify the difference between Zn/NP and Zn/nanocomposite, and also the composition of these coatings. Authors must demonstrate the formation of these nanosystems! For example, by UV-Vis absorption spectra, it could be observed the spectral fingerprint of metal nanoparticles: the SPR band! Moreover, the nanoparticles synthesis could be proved also by microscopy (SEM or TEM or AFM).
I have indicated some comments and corrections in the attached pdf text. Authors must pay attention to the words/paragraphs yellow highlighted.
Comments for author File: 
Comments.pdf
Author Response
We would like to thank the referee for their comments, and we are pleased to improve the manuscript according to suggestions. We have provided a point-by-point response below to feedback and have modified the text and figures accordingly (shown in the manuscript in RED).
This research study is interesting and it could be published after a minor revision. I mentioned in text some observations/corrections/suggestions as follows:
The main aim of the communication is to assess the anticorrosion and tribological properties of metallic coating, with the main focus on the application of confocal laser scanning microscopy (CLSM). To the best knowledge of the authors, this is the first report proving that CLSM could be a valuable tool to study in-depth the details of tribological wear of coatings. To fully deploy the abilities of CLSM the two types of materials – the traditional electroplated zinc-based coating, and the coating obtained the same way but with the addition of nanoparticles (composite one) were investigated. The nanocomposite coating was obtained from the commercial bath Zinc Plating (Gateros Plating Ltd.) with the plating additive provided by coat-it sp. z o. o. The manufacturing and optimisation of the composite coating was not a focus of the current paper.
Additionally, the composition of the additive is a trade secret of the coat-it sp. z o. o. company and cannot be revealed. The paper was amended to put emphases on the above. The detailed answers to reviewer comments are below.
Lines 12-19: the “Abstract” must be improved, by introducing more details about the nanocomposites.
The Abstract was changed, taking into account the comment of the reviewer and the above statement.
Lines 22-39: The section “Introduction” must be improved, and then the section “References” must be updated.
Introduction part was amended, and new references were added. However, as this manuscript is communication, not a full paper, the length of the paper and the number of new references must be kept to a minimum.
The answers to the undermentioned comments were added collectively below:
Line 42: Authors must specify the type of nanoparticles in “metal oxide hard nanoparticles”.
Authors must give more details about the preparation of nanoparticles: method, type etc. and they must insert a reference from scientific literature.
Line 46: Authors must specify the components of these Zn nanocomposites.
Lines 161-162: Authors must specify the type of nanoparticles, the type of additive, and also the correct name of the company in the sentence: “Nanoparticles were introduced into coating by applying the plating additive provided by the coat-it company.”
Line 168: Authors must specify the type of nanoparticles they used in this study.
The authors did not demonstrate the obtaining of nanoparticles and did not specify what type of nanoparticles they used.
Authors must prove the formation of nanoparticles!
Authors must demonstrate the formation of these nanosystems! For example, by UV-Vis absorption spectra, it could be observed the spectral fingerprint of metal nanoparticles: the SPR band! Moreover, the nanoparticles synthesis could be proved also by microscopy (SEM or TEM or AFM).
The preparation of nanoparticles was not the main focus of the presented paper. Formation and composition of this additive is the company secret and cannot be reveal. The paper was amended to reflect the use of CLSM and commercial products to produce zinc nanocomposite coatings, which is the novelty in terms of coatings manufacturing and analysis.
Line 47: Authors must specify the type of additive. Authors must also specify the correct name of “coat-it company”.
The type of additive and the correct name of the company were introduced into the manuscript.
Line 132: Replace “rougnes” with "roughness".
The typographical error has been corrected.
Lines 133-135: Authors must reformulate the sentence:
“Microscopic analysis of friction marks, presented in Fig. 5 and 6, allows to conclude that as a result of sliding wear debris accumulated, which remained in the wear area, and led to intensification of second wear processes.”
The sentence was rewritten. Amended version can be seen below.
Microscopic analysis of friction marks, presented in Fig. 5, show that wear debris accumulated on the surface as a result of sliding. Therefore, remaining in the wear area, these scraps led to intensification of second wear processes.
Line 149: What is the difference between Figures 7A and 7B, and between Fig. 7C and 7D? Please correct the legend of Fig.7:
A, C - Zn coating;
B, D - Zn nanocomposite coating
According to reviewer suggestion we corrected the legend of figure 6 (in the previous version, Fig. 7).
Line 167: The word “of” must be deleted in: “to optimise of the coating composition”.
The word ‘of’ was deleted.
Line 180-198: I observed very few references!
New references were added (please see below). However, their number was limited since this manuscript is communication.
- Mohammadnejad M., Habibolahzadeh A., Yousefpour M., Effect of Nano Oxide Addition on Corrosion Performance of Hot Dip Zinc Coating, Pot Met Phys Chem, 2016, 52, 100.
- Conrad H., Golden T., Electrodeposited Zinc-Nickel Nanocomposite Coatings, Nanocomposites – Recent Evolutions, 2018, IntechOpen.
Authors must specify the difference between Zn/NP and Zn/nanocomposite, and also the composition of these coatings.
There is no difference between Zn/NP and Zn/nanocomposite. It is the same coating. Naming of this coating was unified.
I have indicated some comments and corrections in the attached pdf text. Authors must pay attention to the words/paragraphs yellow highlighted.
The authors edited/improved the parts marked by the reviewer in yellow.
Reviewer 3 Report
The authors has introduced the electroplated method of zinc based nanocomposite coatings, this topic is interesting to the readers of MDPI Coatings but it seems there are several comments which need be addressed properly to understand this manuscript clear.
1/ In introduction, the authors have explained the advantages of Zinc coating but it is still unclear why this Zinc coating is still better than aluminum coating ? And how can the addition of chromium improve this coating? It is still unclear to the readers why the introduction of “solid hard” nanoparticles can improve these coatings.
2/ Explanation of “solid hard” nanoparticles is not clear enough, what do the authors mean with this description? The description of nanoparticles are very limited in this manuscript; It is not clear which type/morphology/crystalline/size of nanoparticles are introduced in this work. This information should be given with an explanation.
3/ Section of Materials and methods should be divided in several subsections to have a good overview.
4/ Material description is very unclear to the readers, it is important that the readers can redo your experiments. For example which type of nanoparticles are introduced and which supplier..
5/ The authors have mentioned in line 103-104 that it is clear on Figure 2 but it is still not clear to the readers. Therefore, adjustments of Figure 2 is necessary.
6/ Figure 3 and 4 (both number II), the text are too small to read.
7/ Based on the results shown on Table 4, it doesn’t show an significant improvement due to the addition of nanoparticles. Which amount of nanoparticles was used in this work? Is there a relation between the properties and the type of nanoparticles?
8/ What is a x-ray microanalysis (EDS) on line 146?
9/ typo line 158: Zn/nanocomposite
10/ General conclusion, the tribological study of these coatings show interesting results but the authors should highlight these improvements more in details because it seems that the addition of nanoparticles doesn’t show a significant improvement. Therefore, more explanation and description of nanoparticles are needed to improve this manuscript.
Author Response
We would like to thank the referee for their comments, and we are pleased to improve the manuscript according to suggestions. We have provided a point-by-point response below to feedback and have modified the text and figures accordingly (shown in the manuscript in RED).
The authors has introduced the electroplated method of zinc based nanocomposite coatings, this topic is interesting to the readers of MDPI Coatings but it seems there are several comments which need be addressed properly to understand this manuscript clear.
1/ In introduction, the authors have explained the advantages of Zinc coating but it is still unclear why this Zinc coating is still better than aluminum coating ? And how can the addition of chromium improve this coating? It is still unclear to the readers why the introduction of “solid hard” nanoparticles can improve these coatings.
The explanation of the influence of nanoparticles on coatings’ properties was included in the Introduction part. Please see added sentences below.
The nanoparticles fill voids in zinc matrix, providing barrier properties by blocking active sites for corrosion initiation [7]. In terms of enhancing mechanical properties, the nanoparticles dispersed in the coating can hinder the easy movement of dislocations, thus increasing coating’s hardness [8].
Chromium compounds are used to increase corrosion resistance of zinc coatings by creating a passive layer on their surfaces. This is an additional barrier layer, which delays white rust formation. The manuscript was amended by adding following sentence:
An additional barrier layer is created.
Indeed, aluminium coatings have better corrosion properties than zinc coatings. However, aluminium is softer and more expensive than zinc, and aluminium coatings cannot be produced by electroplating. Thus, there is no comparison between electroplated zinc coatings and hot-dip aluminium coatings in this manuscript.
2/ Explanation of “solid hard” nanoparticles is not clear enough, what do the authors mean with this description? The description of nanoparticles are very limited in this manuscript; It is not clear which type/morphology/crystalline/size of nanoparticles are introduced in this work. This information should be given with an explanation.
The main aim of the communication was to characterise properties of the metallic coating emphasising the application of confocal laser scanning microscopy (CLSM). The manufacturing and optimisation of the nanocomposite coating were not a focus of the current paper. The “solid hard” nanoparticles were introduced to the coating by using the commercial plating bath additive provided by coat-it sp. z o. o. It is the trade secret of the coat-it sp. z o. o. company, hence cannot be revealed. However, the additional details on the coatings preparation were introduced to the paper to allow the reproduction of the described experiments.
3/ Section of Materials and methods should be divided in several subsections to have a good overview.
As suggested by the reviewer the Materials and Methods section was divided into the subsections.
4/ Material description is very unclear to the readers, it is important that the readers can redo your experiments. For example which type of nanoparticles are introduced and which supplier.
Materials and methods part was edited as suggested.
Coatings were prepared by electrodeposition from acidic bath of 5 litres, containing zinc sulphate as a source of zinc ions, provided by Gateros Plating Ltd. Bath temperature of 20°C and current density of 2 A/dm2 were applied. In case of zinc nanocomposite coatings, the process parameters were kept the same and to the 5 l of standard plating bath 250 ml of nanoparticle containing KA 201 additive provided by coat-it sp. z o. o. (Poland) was added.
5/ The authors have mentioned in line 103-104 that it is clear on Figure 2 but it is still not clear to the readers. Therefore, adjustments of Figure 2 is necessary.
According to reviewer suggestion we added the additional description of figure 2. We have also changed the figure 2 to clearly show the difference between corrosion of investigated coatings.
6/ Figure 3 and 4 (both number II), the text are too small to read.
The figure was edited as suggested.
7a/ Based on the results shown on Table 4, it doesn’t show an significant improvement due to the addition of nanoparticles.
The microhardness of zinc coatings was about 110 HV, in the case of composite coatings the hardness increased to about 120 HV. Thus, an increase of about 9% in hardness was observed, which seems to be a significant improvement in future applications of the composite coating on an industrial scale. The abrasion resistance of new composite coatings is also higher than that of traditional zinc coatings.
Following sentence was added to the manuscript:
The increase of around 9% is a significant improvement in future applications of the nanocomposite coatings at an industrial scale.
7b/ Which amount of nanoparticles was used in this work? Is there a relation between the properties and the type of nanoparticles?
The details regarding the amount of additive used to obtain the nanocomposite were added to the manuscript. Only one type of nanoparticles was used in this study, so it is not possible to conclude the relation of the nanoparticles type and the coating properties. However, based on the published literature, it is known that the properties of nanocomposite coatings depend on the type of nanoparticles.
8/ What is a x-ray microanalysis (EDS) on line 146?
X-ray microanalysis is also called Energy-dispersive X-ray spectroscopy (EDS). It is an analytical technique used for chemical characterization of a sample. The full name of the analytical method used was introduced to the publication.
9/ typo line 158: Zn/nanocomposite
Naming of coatings was unified.
10/ General conclusion, the tribological study of these coatings show interesting results but the authors should highlight these improvements more in details because it seems that the addition of nanoparticles doesn’t show a significant improvement. Therefore, more explanation and description of nanoparticles are needed to improve this manuscript.
The optimisation of the nanocomposite coatings were not a focus of the current studies. Authors applied the commercial zinc plating bath and additive containing nanoparticles to obtain composite coatings. This material was tested further for anticorrosion and tribological features. The improvement achieved in presented research can have significant importance at industrial scale. It is worth to highlight that presented amendment was achieved by employing commercially available products (not experimental composition), which can be used directly at a massive scale.
The details of the additive composition are the trade secret of the company and therefore, cannot be revealed. However, it is worth to notice that the commercially available additive allowed to improve the properties of the standard zinc-based coating. The optimisation of the plating process, and therefore coatings' properties, will be conducted in the future to assure their further improvement.
Round 2
Reviewer 1 Report
The introduction part needs to develop yet.
Author Response
We would like to thank the referee for their comment. We have provided a response below to feedback and have modified the text (shown in the manuscript in RED).
The introduction part needs to develop yet.
Introduction part was amended. However, as this manuscript is communication, not a full paper, the length of the paper and the number of new references must be kept to a minimum.
Reviewer 3 Report
The authors have answered good on my comments, I'm pleased to suggest this manuscript for a publication in Coatings.
Author Response
The authors have answered good on my comments, I'm pleased to suggest this manuscript for a publication in Coatings.
We would like to thank the referee for their comment.
