Hybrid Coating of Polystyrene–ZrO₂ for Corrosion Protection of AM Magnesium Alloys

Round 1

Reviewer 1 Report

ln this manuscript the anticorrosive outcome of polystyrene-ZrO2 coated magnesium alloy and its nanocomposite surfaces in a simulated marine environment is presented. The physicochemical properties of the coating before and after use, and the associations with anticorrosion indices were analyzed and discussed. The conclusion is supported by the experimental data. Suggestions for this contribution are as follows.
1 During 30 days of immersion test (Line 157), the sample is kept static or moving?
2 Figure 1 (c), (d), no "an air" is observed.
3 Figure 3 (a), (b), where does the upper Epoxy come from.  And as a comparison, in Figure 14, the hybrid coating of PS-ZrO2 (central zone) disappears. Is it peeled into the simulated marine environment solution?
4 In Figure 9, Time (Days) is redundant.

Author Response

Reviewer 1: ln this manuscript the anticorrosive outcome of polystyrene-ZrO2 coated magnesium alloy and its nanocomposite surfaces in a simulated marine environment is presented. The physicochemical properties of the coating before and after use, and the associations with anticorrosion indices were analyzed and discussed. The conclusion is supported by the experimental data. Suggestions for this contribution are as follows.

1. During 30 days of immersion test (Line 157), the sample is kept static or moving?

Comment: The sample is kept in static conditions.

2. Figure 1 (c), (d), no "an air" is observed.

Comment: The air bubbles are not visible, however were suggested that there is an air, probably trapped inside the micro/nano-structures of the coating.

3. Figure 3 (a), (b), where does the upper Epoxy come from.  And as a comparison, in Figure 14, the hybrid coating of PS-ZrO2 (central zone) disappears. Is it peeled into the simulated marine environment solution?

Comment: 

The tested samples were embedded in epoxy resin to carry out the cross-section images (Figure 3a,b). At 30 days of exposure (Figure 14a,b) the zone corresponding to the hybrid material is still present on the substrates, as confirmed by the mapping of the elements in Figure 11, where the main constituents of the  are showed.

4. In Figure 9, Time (Days) is redundant.

Comment: The figure was modified.

Reviewer 2 Report

This manuscript reports that hybrid material polystyrene (PS) - ZrO2 was deposited on the surfaces of AM60 and AM60-AlN nanocomposites by spin coating method, and the corrosion resistance of the coating was tested after exposed to SME solution. However, there are still a few following questions that need to be further explored.

1. After 30 days of exposure to SME solution, high-density cracks appear on the surface of the coating, causing a certain degree of erosion of the substrate. It seems that the coating is beginning to lose its protective function. Can the coating process continue to improve in future? Or can it truly be applied in the marine environment? The article lacks prospects for these aspects, so i suggest authors add a brief explanations.

2. Adding cross-sectional images of uncoated samples in Figure 14 for better comparison.

Quality of English is OK.

Author Response

Reviewer 2: This manuscript reports that hybrid material polystyrene (PS) - ZrO2 was deposited on the surfaces of AM60 and AM60-AlN nanocomposites by spin coating method, and the corrosion resistance of the coating was tested after exposed to SME solution. However, there are still a few following questions that need to be further explored.

1. After 30 days of exposure to SME solution, high-density cracks appear on the surface of the coating, causing a certain degree of erosion of the substrate. It seems that the coating is beginning to lose its protective function. Can the coating process continue to improve in future? Or can it truly be applied in the marine environment? The article lacks prospects for these aspects, so I suggest authors add a brief explanation.

Comment:

In the conclusions, a text was added. “The corrosion protective efficient of the hybrid  against the presence of chlorides should be improved by modifying the concentration of the precursors, and/or applying a drying process that use temperature program ramp.”

2. Adding cross-sectional images of uncoated samples in Figure 14 for better comparison.

Comment:

The Figure 14 was modified by attaching images of uncoated samples.

Reviewer 3 Report

The authors studied the hybrid coating of polystyrene-ZrO2 for corrosion protection of AM magnesium alloys.

 There are several problems to be addressed:

1.       In the introduction section there is too much detailed information about the methods for evaluating the properties of the materials under study. This should be moved to the section 2 Materials and methods.

2.       The authors should add some more information in introduction regarding the goal of the research.

3.       Can the authors of the study explain the presence of microdefects in the coatings, which by forming a channel can worsen the corrosion properties of the material? How can the defects formation be minimized?

4.       4.Figure 10 shows that ZrO2-AM60-AlN and PS-ZrO2-AM60 coatings are characterized by a large number of cracks after 30 days of exposure. For the application of such coatings a longer period of operation than 30 days should be foreseen. Can we conclude that these coatings are not yet appropriate for use as corrosion protection?

5.       I suggest improve the conclusion section. The authors should outline the most appropriate coatings. What type of coating and treatment allows obtaining the coating with best properties?

Minor editing of English language required

Author Response

Reviewer 3: The authors studied the hybrid coating of polystyrene-ZrO2 for corrosion protection of AM magnesium alloys. There are several problems to be addressed:

1. In the introduction section there is too much detailed information about the methods for evaluating the properties of the materials under study. This should be moved to the section 2 Materials and methods.

Comment:

The introduction text was adjusted.

2.The authors should add some more information in introduction regarding the goal of the research.

Comment:

The text was added: “In order to improve the corrosion resistance of AM-magnesium alloys against the presence of chlorides, in this research sol-gel method was applied for the synthesis of the polystyrene-zirconium dioxide ……..”

3. Can the authors of the study explain the presence of microdefects in the coatings, which by forming a channel can worsen the corrosion properties of the material? How can the defects formation be minimized?

Comment:

In the conclusions, a text was added. “The corrosion protective efficient of the hybrid  against the presence of chlorides should be improved by modifying the concentration of the precursors, and/or applying a drying process that use temperature program ramp.”

4. Figure 10 shows that ZrO2-AM60-AlN and PS-ZrO2-AM60 coatings are characterized by a large number of cracks after 30 days of exposure. For the application of such coatings a longer period of operation than 30 days should be foreseen. Can we conclude that these coatings are not yet appropriate for use as corrosion protection?

Comment:

In the conclusions, a text was added. “The corrosion protective efficient of the hybrid  against the presence of chlorides should be improved by modifying the concentration of the precursors, and/or applying a drying process that use temperature program ramp.”

5. I suggest improve the conclusion section. The authors should outline the most appropriate coatings. What type of coating and treatment allows obtaining the coating with best properties?

Comment:

In the conclusions, a text was added. “The corrosion protective efficient of the hybrid  against the presence of chlorides should be improved by modifying the concentration of the precursors, and/or applying a drying process that use temperature program ramp.”