Concentration Influence of Complexing Agent on Electrodeposited Zn-Ni Alloy

Round 1

Reviewer 1 Report

The authors reported that the effect of TEPA concentration on the Ni content in the electrodeposited Zn-Ni coating film in detail. The work can be accepted after minor revision according to the following suggestions.

1. The Figure 2 should be modified, the texts in Figure are too small.

2. The Figure 3, Figure 5, Figure 6 and Figure 7 can be modified for better understanding.

 

Author Response

We would like to thank you for your kind comments. We carefully considered your comments and modified our manuscript accordingly. Please find our point-to-point response below. We also corrected the content following the reviewers’ comments and the revised parts are shown in red in the manuscript.

#Reviewer 1:

The authors reported that the effect of TEPA concentration on the Ni content in the electrodeposited Zn-Ni coating film in detail. The work can be accepted after minor revision according to the following suggestions.

1. The Figure 2 should be modified, the texts in Figure are too small.

Reply: The sentence was edited as pointed out.

 

2. The Figure 3, Figure 5, Figure 6 and Figure 7 can be modified for better understanding.

Reply: The sentence was edited as pointed out.

Author Response File: Author Response.docx

Reviewer 2 Report

Zn-Ni alloys can be used as a sacrificial coating to protect stainless steel. The authors investigated the effect of TEPA concentration on the electrodeposited Zn-Ni alloy coating. The appearance, surface gloss, microstructure and thickness of the obtained Zn-Ni coatings are examined and analized in this manuscript. This work has been systematically studied and some useful conclusions have been drawn. I recommend its acceptance for publication. There are some suggestions for improvement.

1. It is recommended to add a flowchart or schematic diagram of the electrolysis process.

2. Figure 6bc is deformed.

3. The scales in Figure 7are too small.

4. In addition to their effects, further discussion should be added on the mechanism of complexing agents.

5. There are too many qualitative descriptions in the conclusion, which need to be changed to quantitative descriptions.

The overall English expression is fluent, it is recommended to carefully be checked again.

Author Response

Response to the reviewers’ comments

 Concentration influence of complexing agent on electrodeposited Zn-Ni alloy

We would like to thank you for your kind comments. We carefully considered your comments and modified our manuscript accordingly. Please find our point-to-point response below. We also corrected the content following the reviewers’ comments and the revised parts are shown in red in the manuscript.

#Reviewer 2:

Zn-Ni alloys can be used as a sacrificial coating to protect stainless steel. The authors investigated the effect of TEPA concentration on the electrodeposited Zn-Ni alloy coating. The appearance, surface gloss, microstructure and thickness of the obtained Zn-Ni coatings are examined and analized in this manuscript. This work has been systematically studied and some useful conclusions have been drawn. I recommend its acceptance for publication. There are some suggestions for improvement.

1. It is recommended to add a flowchart or schematic diagram of the electrolysis process.

Reply: The sentence was edited as pointed out.

 

2. Figure 6bc is deformed.

Reply: The sentence was edited as pointed out.

 

3. The scales in Figure 7are too small.

Reply: The sentence was edited as pointed out.

 

4. In addition to their effects, further discussion should be added on the mechanism of complexing agents.

Reply: the explanation was added as follow.

The increase in Ni content owing to TEPA can be explained by the fact that TEPA acts as a complexing agent that binds with Ni ions to prevented the precipitation of Ni hydroxide, thereby enhancing the deposition of metallic Ni on the cathode surface [27,28,34].

 

5. There are too many qualitative descriptions in the conclusion, which need to be changed to quantitative descriptions.

Reply: As suggested, the conclusion was modified as below.

This study aimed to investigate the impact of TEPA concentration on electrodeposited Zn-Ni alloy coatings. The results indicate that an increase in TEPA concentration from 0.035 M to 0.1 M led to the improved surface gloss of coatings at low current densities, as well as an increase in the crystallization of Zn-Ni alloy coating at low current density. While the crystallite size decreased with increasing TEPA concentration, the increase in TEPA concentration resulted in a coarser morphology of the Zn-Ni coating. Additionally, the increase in TEPA concentration led to a decrease in the thickness of coatings from approximately 10 mm to lower than 5 mm at a current density higher than 2 ASD. On the other hand, the variation in Ni content was proportional to the change in TEPA concentration, and the content of Ni could reach up to 20% at 8 ASD and TEPA concentration higher than 0.035 M. Notably, the study found that TEPA concentration did not influence the electrochemical behavior of Zn-Ni alloy deposition. In conclusion, this study highlights the vital role of TEPA concentration in controlling the properties of Zn-Ni alloy coatings. The findings have important implications for the development of high-performance coatings in a range of industrial applications. Further research is needed to explore the underlying mechanisms of the observed effects and identify strategies for further improving the properties of Zn-Ni alloy coatings.

Author Response File: Author Response.docx

Reviewer 3 Report

The subject of the paper is current and ongoing research for galvanic technology, and I congratulate the authors for addressing this aspect of the global process of depositing metals and alloys. As specified in the theoretical part “The addition of additives in electroplating is essential as they impact on the growth and structure of the deposits, thereby enhancing the appearance, and properties of coatings or the performance of bath”.

 

As a reviewer of this article, I have some observations, questions and concerns:

 

Row 48 While cyanide solution is poisonous shows high toxicity for the environment.

 

Row 49 zincate solution possesses  has some advantages

 

Row 52 The typical composition of zincate solution consists of Zn and Ni ions. Please fill in the text with the compounds (salts or oxides) from which these cations come.

 

Row 56 Hydrogen generation evolution reaction (HER) during Zn and Zn alloy electrodeposition

 

Rows 59- 72 For the presented mechanism, in which the metal deposition process takes place simultaneously with HER, please cite the bibliographic sources or specify if this is proposed by you.

Also, please change the ions charge from +2 to 2+.

 

Rows 82 This excellent possession. Please change possession.

For the informations presented in paragraph between 73 and 82, please add bibliographical data. I don't think it is enough to cite a single article.

Row 139 Please explain Ni-CPL

Row 148 Ag/AgCl/KCl electrode was used as a reference electrode. Please specify the potential value of this reference electrode.

Figure 1. Please explain in text ASD.

Row 206 0.07M. Please put space between 0.07 and M. Also in Rows 211 and 213, 225

Page 9 and 10. The graphs in figures 5 and 6 should have the same resolution/size

Rows 320 and 321 Why is the temperature presented in K degree,if up to this point everything has been discussed in Celsius degrees. There should be a unitary presentation. It can remain in C even if it is the thermodynamic temperature for which the value of the equilibrium potential is presented.

 

 

Q1. Why the authors chose 0.035, 0.7, and 1 M values ​​for TEPA concentrations?

Q2. Why the authors use amps/dm2 (ASD) as unit for current density. Can use A/dm2 or A/m2?

Q3. Please explain the term partial polarization curve. And please explain why use for the points presented in figure 8 – partial polarization curves? In the methods part the authors specified electrochemical polarization curves were obtained using a potentiostat/galvanostat (HA-151B, Hokuto Denko, Japan). Where are the polarization curves recorded at the potentiostat and why are the values ​​presented in the form of dissipated points in figure 8? Please explain.

Also, if the authors have chosen the methods “The partial current densities of Zn and Ni electrodeposition were calculated from the mass obtained and the chemical composition of the coating according to Faraday’s laws of electrolysis using the formula…., where i is the partial current density of element.” Please explain how many samples - alloy depositions were performed and at what values ​​of the current densities. Why are the current density values ​​presented on a logarithmic scale?

 

Observation: The influence of the brightening agent on the deposition process of Zn, Ni, or Zn-Ni can be done very easily by drawing some cathodic polarization curves with the potentiostat at the lowest possible polarization speed max 1 mV/s, on the electrode made from the substrate on that the coating is achieved, in the absence or in the presence of different concentrations of the additive.

 

English language is generally fine, minor editing of English language required.

Author Response

Response to the reviewers’ comments

Concentration influence of complexing agent on electrodeposited Zn-Ni alloy

We would like to thank you for your kind comments. We carefully considered your comments and modified our manuscript accordingly. Please find our point-to-point response below. We also corrected the content following the reviewers’ comments and the revised parts are shown in red in the manuscript.

#Reviewer 3:

The subject of the paper is current and ongoing research for galvanic technology, and I congratulate the authors for addressing this aspect of the global process of depositing metals and alloys. As specified in the theoretical part “The addition of additives in electroplating is essential as they impact on the growth and structure of the deposits, thereby enhancing the appearance, and properties of coatings or the performance of bath”.

 

As a reviewer of this article, I have some observations, questions and concerns:

 

Row 48 While cyanide solution is poisonous shows high toxicity for the environment.

Reply: The sentence was edited as pointed out.

 

Row 49 zincate solution possesses  has some advantages

Reply: The sentence was edited as pointed out.

 

Row 52 The typical composition of zincate solution consists of Zn and Ni ions. Please fill in the text with the compounds (salts or oxides) from which these cations come.

Reply: As suggested, the compounds were added as follows

The typical composition of zincate solution consists of Zn and Ni ion compounds, such as ZnO, and Ni₂SO₄. 6H₂O, sodium hydroxide (NaOH), and organic additives[18].

 

Row 56 Hydrogen generation evolution reaction (HER) during Zn and Zn alloy electrodeposition

Reply: The sentence was edited as pointed out.

 

Rows 59- 72 For the presented mechanism, in which the metal deposition process takes place simultaneously with HER, please cite the bibliographic sources or specify if this is proposed by you.

Also, please change the ions charge from +2 to 2+.

Reply: the reference 19 was added.

 

Rows 82 This excellent possession. Please change possession.

Reply: The sentence was edited as pointed out.

This excellent property was attributable to the existence of g phase in the microstructure.

 

For the informations presented in paragraph between 73 and 82, please add bibliographical data. I don't think it is enough to cite a single article.

Reply: As suggested, the references 20 and 21 were added.

 

Row 139 Please explain Ni-CPL

Reply: the potential was supplemented as below

Ni-CPL( 450g/L)

 

Row 148 Ag/AgCl/KCl electrode was used as a reference electrode. Please specify the potential value of this reference electrode.

Reply: the potential was supplemented as below

Ag/AgCl/KCl electrode, which has a potential of 0.197 V versus normal hydrogen electrode, was used as a reference electrode.

 

Figure 1. Please explain in text ASD.

Reply: the figure caption was edited as follow.

Figure 1. (a) Appearance of Zn-Ni alloy coatings obtained by Hull cell test with varying TEPA concentrations, and (b) glossiness as a function of current density (A/dm²) and TEPA concentration, measured in gloss units (GU).

 

 

Row 206 0.07M. Please put space between 0.07 and M. Also in Rows 211 and 213, 225s

Reply: As pointed out, the modification was conducted.

Page 9 and 10. The graphs in figures 5 and 6 should have the same resolution/size

Reply: The sentence was edited as pointed out.

 

Rows 320 and 321 Why is the temperature presented in K degree, if up to this point everything has been discussed in Celsius degrees. There should be a unitary presentation. It can remain in C even if it is the thermodynamic temperature for which the value of the equilibrium potential is presented.

Reply: As pointed out, the modification was conducted.

 

Q1. Why the authors chose 0.035, 0.7, and 1 M values ​​for TEPA concentrations?

Reply: Our group varied several TEPA concentration and noticed that we could obtain the significant change in properties at these concentrations.

 

Q2. Why the authors use amps/dm2 (ASD) as unit for current density. Can use A/dm2 or A/m2?

Reply: ASD is the most common unit used for current density. You can use A/m², or A/cm² if needed.

 

Q3. Please explain the term partial polarization curve. And please explain why use for the points presented in figure 8 – partial polarization curves? In the methods part the authors specified electrochemical polarization curves were obtained using a potentiostat/galvanostat (HA-151B, Hokuto Denko, Japan). Where are the polarization curves recorded at the potentiostat and why are the values ​​presented in the form of dissipated points in figure 8? Please explain.

Also, if the authors have chosen the methods “The partial current densities of Zn and Ni electrodeposition were calculated from the mass obtained and the chemical composition of the coating according to Faraday’s laws of electrolysis using the formula…., where i is the partial current density of element.” Please explain how many samples - alloy depositions were performed and at what values ​​of the current densities. Why are the current density values ​​presented on a logarithmic scale?

Reply: The description was modified as follow.

To investigate the deposition behavior of each component of Zn-Ni alloy, the partial polarization curves of Zn and Ni deposition could be determined using the following method. The content of coulomb (q) was fixed (2.5C), and the current density (i_a) of alloy deposition was varied (0.1, 0.2, 0.5, 1, 2, 5, 10, 20, and 50 ASD); hence, the deposition time was determined as follow t= q/i_a. By applying the determined time and current density, the potential could be recorded using the potentiostat. The partial current densities of each Zn and Ni electrodeposition were calculated from the element mass obtained by AAS and the chemical composition of the coating according to Faraday’s laws of electrolysis using the formula: i, where i is the partial current density of element (A.cm^-2), m is the amount of element (g), M is the molecular weight of element (g/mol), v is the valency of the ions, A is the surface area of the cathode (cm²) t is time of electrodeposition (s), and F is Faraday constant (96 500 s.A/mol). For each sample, the electrochemical test was carried out 3 times, and the average values were calculated. Figure 8 displays the partial polarization curves of Zn and Ni during Zn-Ni alloy electroplating at a room temperature. For the ease of visibility, the current density presented as a function of potential on a logarithmic scale.

 

Observation: The influence of the brightening agent on the deposition process of Zn, Ni, or Zn-Ni can be done very easily by drawing some cathodic polarization curves with the potentiostat at the lowest possible polarization speed max 1 mV/s, on the electrode made from the substrate on that the coating is achieved, in the absence or in the presence of different concentrations of the additive.

Reply: Thank you for your suggestion. In this work, we made the polarization curve from dissipated points without scanning speed. In doing so, we could determine the partial polarization curve of each component deposition, i.e. Zn and Ni, while Zn-Ni alloy deposition was conducted.

 

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Thank you for your responses to the observations made as a reviewer of your scientific paper. These correspond to my requests and the requirements of the MDPI Journal in which you want to publish this work.