Review Reports - The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

Round 1

Reviewer 1 Report

Although the manuscript present an impressive number of references, the manuscript does not follow the PRISMA guidelines for presenting Reviews which is required by MDPI ( https://www.mdpi.com/journal/coatings/instructions ). It is necessary to correct the manuscript using PRISMA checklist: http://www.prisma-statement.org/PRISMAStatement/Checklist , especially Methods should be described.

Some minor issues:

In the text, there are a lot of double spaces. Introduction section: It is quite unclear what is the main purpose and use of the paper. Tables 5 and 6 are not referenced in the text.

4 .Subsections should be written in italics.

Reference list is not formatted according to the Instructions for Authors. Caption of Figure 1: It is necessary to indicate meaning of (a), (b) etc. line 80: “Keller et al.” are not coauthors of reference no. 63. line 182: “Farnan et al.” are not coauthors of reference no. 2. line 185: "Sheasby and Pinner" should be "Wernick et al.". line 875: "McNeice et al." should be "McNeice and Ghahreman".

Author Response

SEALING REVIEW MANUSCRIPT TO COATINGS MDPI AG, REVIWER COMMENTS AND RESPONSES ROUND 1

REVIEWER 1

REVIEWER 1, COMMENT 1:

RESPONSE TO REVIEWER 1, COMMENT 1: Efforts have now been made to make the present version of the manuscript consistent with the PRISMA guidelines for presenting reviews. To this end, section 2, dealing with “ Scope and Methodology of the Review” has now been added.

REVIEWER 1, COMMENT 2:

Some minor issues:

In the text, there are a lot of double spaces. Introduction section: It is quite unclear what is the main purpose and use of the paper. Tables 5 and 6 are not referenced in the text.

RESPONSE TO REVIEWER 1, COMMENT 2: the double spaces were principally due to formatting and have now been taken care of.

The main purpose of the review has now been expressed in section 2 of the review by introduction of the sentence “This systematic review was carried out as a contribution to the quest for post-sealing anodized aluminium with qualities superior to that obtained by hot-water sealing but at temperatures much lower than that used for hot-water sealing and without the use of toxic compounds. ”

Tables 5 and 6 are now referenced in the text.

REVIEWER 1, COMMENT 3:

4 .Subsections should be written in italics.

RESPONSE TO REVIEWER 1, COMMENT 3: Sub-sectional headings have now been italicized.

REVIEWER 1, COMMENT 4:

Reference list is not formatted according to the Instructions for Authors.

RESPONSE TO REVIEWER 1, COMMENT 4: Reference list has now been formatted.

REVIEWER 1, COMMENT 5:

Caption of Figure 1: It is necessary to indicate meaning of (a), (b) etc.

RESPONSE TO REVIEWER 1, COMMENT 5: Caption of Figure 1 has now been modified to indicate meanings of (a), (b), (c), (d), and (e).

REVIEWER 1, COMMENT 6: line 80: “Keller et al.” are not coauthors of reference no. 63.

RESPONSE TO REVIEWER 1, COMMENT 6: Thanks for the observation. The error in attributing references 62 and 63 to Keller et al has now been corrected.

REVIEWER 1, COMMENT 7: line 182: “Farnan et al.” are not coauthors of reference no. 2.

RESPONSE TO REVIEWER 1, COMMENT 7: The error has now been corrected. It was supposed to be Farnan et al., [80,81]. Correction has now been effected.

REVIEWER 1, COMMENT 8: line 185: "Sheasby and Pinner" should be "Wernick et al.".

RESPONSE TO REVIEWER 1, COMMENT 8: The error in the name attributed to the reference has now been corrected from "Sheasby and Pinner" to "Wernick et al.,".

REVIEWER 1, COMMENT 9: line 875: "McNeice et al." should be "McNeice and Ghahreman".

RESPONSE TO REVIEWER 1, COMMENT 9: The error in the attribution for Ref;378 has now been corrected from "McNeice et al." to "McNeice and Ghahreman".

Author Response File: Author Response.pdf

Reviewer 2 Report

Table 1. Please, write the chemical formula of sodium sulphate, sulphuric acid, nickel fluoride, Nickel acetate, Sodium acetate, sodium or ammonium salt, Cerium nitrate, cerium chloride, Na₂MoO₄, Sodium silicate, yttrium
sulphate and etc.

At the first time, you write name and formula of chemical compounds, for example, boehmite (AlOOH), further you write only formula - AlOOH.

The "Bath operating conditions" write at different style, sometimes you write full information, sometimes you write only numeric characteristics 2.5 g/l NiF₂, 25 °C, 30 min. You must use one style.

... EIS spectra ... EDS analysis in TEM images ... GPTMS... TPOZ...LDH...TEA write the full name of this abbreviatures.

What kind of measurement gdm^-3?

Chapter 2. It is necessary to add a figure of types of co-ordination of Al cations with oxygen anions end etc.

Whats about chemical reactions in this chapter?

Figure 2, 3, 4. It is a bad quality scan copy from an old article or book, It is necessary to re-write this picture.

Table 2. If this value from one reference you can add this information in the title of the table and delete excess column.

Table 3. Mechanism. Different style at chemical reactions. You write some reactions at ions form, sometimes full formula. You don't write the form of compounds - solid, liquid or gas.

Some species write in grey colour. It looks very bad. Change to another colour: green, blue and etc.

Line 348. boehmite and bayerite chemical formula write incorrectly. You must change Al2O3.H2O to Al2O3·H2O. This mistake I see in all paper.

Figure 6. This figure is really good quality! It has different colours, it is very simple to understand your idea by look for this figure.

Table 5. Solubility product constants. This value doesn't write in the middle of the column.

Table 6. Why you write twice about Alumina and three times about boehmite? What type of second type of alumina? alfa or gamma?

Many words have been written in the abstract, introduction and conclusions about energy efficiency. However, the article itself does not say anything about energy consumption when applying various sealing methods. The conclusions are very general. Which method do you propose to use? Please, write the basic technological parameters. After reading your article, I received a lot of information, however, it is difficult for me to understand which method is the most. I did not see clearly the criteria by which these methods were compared.

The article itself contains a huge number of sources. This is a positive point. However, the text itself is written carelessly. Many gaps, omissions (as in reactions 1-2). Some of the words are capitalized, some are small. Coatings style not sustained. All tables must be redesigned according to the requirements of the journal. The same applies to the list of references. Please, use Mendeley or Endnote for this.

Globally, I have 2 questions for authors:
1. Why you submitted this paper to the Coating? I think Metals are better for this article?
2. Why is it necessary to pay so much attention to such an insignificant operation?

Author Response

SEALING REVIEW MANUSCRIPT TO COATINGS MDPI AG, REVIEWER 2 COMMENTS AND RESPONSES TO COMMENTS ROUND 1

REVIEWER 2

REVIEWER 2, COMMENT 1:

RESPONSE TO REVIEWER 2, COMMENT 1: The chemical formulas of the mentioned chemical compounds have now been inserted into Table 1.

REVIEWER 2, COMMENT 2:

At the first time, you write name and formula of chemical compounds, for example, boehmite (AlOOH), further you write only formula - AlOOH.

RESPONSE TO REVIEWER 2, COMMENT 2: The bracket was used in instances where both the name and the chemical formula are presented.

REVIEWER 2, COMMENT 3:

The "Bath operating conditions" write at different style, sometimes you write full information, sometimes you write only numeric characteristics 2.5 g/l NiF₂, 25 °C, 30 min. You must use one style.

RESPONSE TO REVIEWER 2, COMMENT 3: Error has been corrected and the style harmonized all through the manuscript

REVIEWER 2, COMMENT 4:

... EIS spectra ... EDS analysis in TEM images ... GPTMS... TPOZ...LDH...TEA write the full name of this abbreviatures.

RESPONSE TO REVIEWER 2, COMMENT 4: Full names of these abbreviations have now been added in the text, particularly in the Tables.

REVIEWER 2, COMMENT 5:

What kind of measurement gdm^-3?

RESPONSE TO REVIEWER 2, COMMENT 5: The format for units have now been changed and harmonized in the test. The unit now reads, g/dm³.

REVIEWER 2, COMMENT 6:

Chapter 2. It is necessary to add a figure of types of co-ordination of Al cations with oxygen anions end etc.

RESPONSE TO REVIEWER 2, COMMENT 6: Schematic illustration of the three ways in which aluminium cations coordinate with oxygen anions in the porous anodized alumina layer on anodized aluminium has now been added to the current version of the manuscript.

REVIEWER 2, COMMENT 7:

Whats about chemical reactions in this chapter?

RESPONSE TO REVIEWER 2, COMMENT 7: Chemical reactions have now been rewritten using Microsoft Equation tool.

REVIEWER 2, COMMENT 8:

Figure 2, 3, 4. It is a bad quality scan copy from an old article or book, It is necessary to re-write this picture.

RESPONSE TO REVIEWER 2, COMMENT 8: All the Figures mentioned have now been enhanced.

REVIEWER 2, COMMENT 9:

Table 2. If this value from one reference you can add this information in the title of the table and delete excess column.

RESPONSE TO REVIEWER 2, COMMENT 9: Thanks for this observation. The column has now been deleted and the mono-source of binding energy data acknowledged in a footnote to Table 2.

REVIEWER 2, COMMENT 10:

Table 3. Mechanism. Different style at chemical reactions. You write some reactions at ions form, sometimes full formula. You don't write the form of compounds - solid, liquid or gas.

Some species write in grey colour. It looks very bad. Change to another colour: green, blue and etc.

RESPONSE TO REVIEWER 2, COMMENT 10: Purple colour has now been used for the species formally presented in gray colour. Chemical reactions have now been rewritten using Microsoft Equation tool. In some instances, equations have been presented slightly differently to highlight surface reactions. In a few other cases, information from references cited does not permit assumptions that are necessary to present equations differently.

REVIEWER 2, COMMENT 11:

Line 348. boehmite and bayerite chemical formula write incorrectly. You must change Al2O3.H2O to Al2O3·H2O. This mistake I see in all paper.

RESPONSE TO REVIEWER 2, COMMENT 11: The error in the placement of the “dot” in the chemical formulas have now been corrected.

REVIEWER 2, COMMENT 12:

Figure 6. This figure is really good quality! It has different colours, it is very simple to understand your idea by look for this figure.

RESPONSE TO REVIEWER 2, COMMENT 12: Thanks for your appreciation of the figure.

REVIEWER 2, COMMENT 13:

Table 5. Solubility product constants. This value doesn't write in the middle of the column.

RESPONSE TO REVIEWER 2, COMMENT 13: It was a formatting issue and has now been addressed.

REVIEWER 2, COMMENT 14:

Table 6. Why you write twice about Alumina and three times about boehmite? What type of second type of alumina? alfa or gamma?

RESPONSE TO REVIEWER 2, COMMENT 14: This as reported in the referred works for the properties of the aluminium oxide phases. The second type reported thrice are values of the gamma from 3 different sources.

REVIEWER 2, COMMENT 15:

RESPONSE TO REVIEWER 2, COMMENT 15: Thanks so much for this comment. Though the new insights presented which aims to reduce sealing bath temperature and thus are to improve the energy efficiency, this was not sufficiently demonstrated.

A new section (section 11 in the current version) has now been added and the magnitude of energy saving envisaged from proffered plausible solutions as a function of reduction in bath operating temperature is now presented based on calculations for a 5,000 litre industrial scale sealing bath.

REVIEWER 2, COMMENT 16:

RESPONSE TO REVIEWER 2, COMMENT 16: Tables have now been redesigned. Chemical equations have now been rewritten using the Microsoft equation editor. The reference list has now been addressed.

REVIEWER 2, COMMENT 17:

Globally, I have 2 questions for authors:
1. Why you submitted this paper to the Coating? I think Metals are better for this article?

RESPONSE TO REVIEWER 2, COMMENT 17: The manuscript was submitted to coatings because it dealt mainly with improvement of the properties of the oxide coating on anodized aluminium surface. We had thought that Metals was more suited to work on bulk processing and bulk properties of metals. This assumption, informed submission of the manuscript to Coatings

REVIEWER 2, COMMENT 18:
2. Why is it necessary to pay so much attention to such an insignificant operation?

RESPONSE TO REVIEWER 2, COMMENT 18: The sealing step is not an insignificant operation. Without appropriate sealing the anodized aluminium product cannot be used in most of the applications it is used in today due to reduction in its durability, aesthetics over a long time, and corrosion resistance. For instance, by appropriate sealing up to 3-fold improvement in corrosion resistance can be achieved compared to anodized but unsealed aluminium products.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have adequately addressed my comments and suggestions, and I feel that this manuscript is now acceptable for publication. I am comfortable with the modifications made by the authors.

Reviewer 2 Report

The authors did a good job of the mistakes. Tables are much better. A new figure 8 has been added.

There are several flaws in the article:

1) the style of Temperature writing the temperature is different everywhere. Need to fix it. This is a small remark. The editor will fix it.

2) In the abstract, very general words are written. Perhaps you need to add more numbers and chemical compounds and reduce the amount of text. You write the phrase: ... in the past 30 years on the sealing process ... It is necessary to specify the period. e.g. 1990-2020. Because in a few years this phrase will not be relevant.