Experiences with Thermal Spray Zinc Duplex Coatings on Road Bridges
Round 1
Reviewer 1 Report
Dear Authors,
I have read Your work with great attention and interests. The submission falls within the scope of the journal and the work is sufficiently original.
I have a lot of remarks and comments to preparation of the manuscript, so I recommend to publish it after major revisions.
General remarks:
In my opinion, the manuscript differs from typical papers published in scientific journals (eg Mdpi) because it does not treat the production and performance of coatings in laboratory conditions, but about their use in natural conditions. The work shows the effects of the influence of long-term environmental factors. Unfortunately, the article is composed a bit chaotically and requires thorough additions to increase its cognitive and especially scientific values.
In the Introduction, please add a paragraph regarding the desirability of undertaking the research by citing works describing eg effects of bridge failure, duplex coating manufacturing, degradation of sprayed coatings. This will allow better introduction in the article and at the same time will improve the quality of the references.
Above all, the presentation of research methodology needs to be supplemented. In my opinion, it is necessary to change sub-chapters 2.1 and 2.2. In 2.2 additional information should be given about: location of bridges (I suggest a map with marked locations), the operating conditions that may affect the durability of the coatings (height, intensity of traffic, direction of the bridge: S-N, E-W). Names of bridges appear suddenly in the further part (line 107) of the article and are unknown to the readers from outside Norway.
Were the exploitation conditions industrial, anthropogenic or natural (wild fjords :))? How was the distance between the bridges? Can meteorological data be used to describe the operating conditions? On what basis did the research sites be selected? Why are these bridges studied? Are these all bridges? How many similar bridges?
The work is actually a technical report. The scientific level would raise the answer to the question: can the durability of the coatings be predicted based on the test results?
References are too few for a scientific article in a renowned journal. In addition, there is a lack of works from Coatings, and yet the journals from the MDPI publishing house are known for the fact that articles often form a cycle, which favors a scientific discussion.
Detailed remarks:
Delete spaces before brackets []
Line 37: expand the shortcut; line 47 remove it
Lines 61-64: this is summary before investigations
Line 94: add reference to given categories
Line 117: change 3,5 to 3.5 and change % to ‰ (in line 116 too)
Line 120: Chapter 2 lacks information on the scope of research. How many bridges were tested in each stage?
Line 126: change “costal” to “coastal”
Table 2. Could registered temperature changes (3-8) affect the results?
Line 186: change font size
Table 3: correct “Corrosivity”, “Condition” and “Maintenance”. On what basis has the conditions been assessed: good and fair?
Figure 2: the Y axis description is missing
Line 214: add reference for the equation
Figure 3 b: How were the error bars counted? Why is the error for the first C2 bar so big?
Figs 4-7 are too poorly described. Please insert information (arrows).It is not known where the images are from. How were the samples digested? Fig. 5: layers and defects must be determined and descibed.
Conclusions should be reworded to highlight the results obtained.
Author Response
A paragraph has been added to the introduction about the history and use of duplex coatings on bridges around the world to underline the importance of the study. Bridges rarely fail due to extensive maintenance, so there are few such studies. Duplex coating manufacture is not complicated and assumed to be known to the Reader. Degradation of TSZ Duplex coatings have not been thorughly studied and to Our knowledge there are no other studies on this subject than the ones already cited.
Section 2.1 and 2.2 have been revised. More details are given in Section 2.1. In Section 2.2 a map is given With all bridge locations plotted. Estimation of corrosivity has been explained. Section 2.4 is added to explain the coating performance indicator (CPI)
Corrosivity was determined by geography, climatic conditions and height above water as explained in section 2.2 and 3.2. Distance between bridges is shown in the map in figure 1. Methrological conditions are not available for the bridges, only general information for the regions and spot measurements at methrological stations. The bridges were selected as explained in section 2.2. Only bridges are included in the study. There are many similar bridges in Norway and the rest of the world.
This paper discusses coating performance based on Field experiences, not test results. Correlation to Laboratory results is Beyond the Scope of this work. Field performance of coatings and description of degradation mechanisms acting in the Field is important for R&D on coatings. In Our opinion, studies like this one is important to Direct coating reasearch to the relevant topics.
More References has been added. There are no relevant papers to cite in Coatings.
The paper is revised according to the detailed remarks
Author Response File: 
Author Response.docx
Reviewer 2 Report
Line186, the font size is smaller than rest of text “The Bergsøysundbrua”
Line 206 Figure 2, define the x and y axis in plots
Line 214-218, It is better to make a table to present C and S numbers for calculation of CPI
Line 244, there is a spelling mistake. “thickness, i.e. both TSZ and pant”
Line 266, Figure 4 and 6 has no scale bar in image
Line 287, what is the sufficient film thickness. The author refers many times about the limitation of film thickness. Please define the range of proper film thickness.
Line 320, Please define the NPRA in text.
Line 358, author claimed the difference of coating performance is due to application errors. Please suggests different suggestions to avoid these problems and improve coating performance.
Author Response
Line 186: Changed
Line 206: Y-axis is defined. X-axis is self explanatory
Line 214-218: C and S numbers are given in Table 4 and 5
Line 244: Pant corrected to Paint
Line 266: Scale bars added
Line 287: Discussion of sufficient film thickness added to section 4.1
Line 320: NPRA was defined in the abstract and the introduction
Line 358: Summary of suggestions have been added
Reviewer 3 Report
The paper is sound and logic.
Despite of some minor spellchecking (e.g. page 14 line 383: change" have" to "has"), no revision are requested.
Author Response
Line 383: Changed have to has
Round 2
Reviewer 1 Report
Dear Authors,
Thank you very much for considering my comments, especially adding a map (it showed how extensive the presented analyzes are) and supplementing the description of the research and photos. I think that the article in its present form will be valuable to the readers of Coating journal. Indeed, the subject of the article is relatively rare and hermetic and it is difficult to find a large number of references. We can count on this article to be a source of inspiration for further researchers in similar issues. I wish you this!
