Assessment of the Residual Life of the Repaired Arousa Bridge
, Diego Carro-López 2,*, Manuel F. Herrador 2 and Javier Eiras-López 2Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors present a case study of the substructure of a coastal bridge that has received galvanic cathodic protection (GCP) including measurements after a considerable time of operation, interpreted in terms of residual working life of the GCP system. An interesting detail is that it also is a hybrid system with an initial impressed current phase that subsequently operates as a galvanic (sacrificial) system.
Case studies like this are important for users and consultants who have to deal with existing structures in aggressive environment, as (hybrid) GCP is one of possible techniques to extend their service lives. However, the question of their working life remains uncertain as any numbers from ten years to several decades have been proposed. In addition, proposers of hybrid systems claim advantages that have not always been documented well.
In general the manuscript provides some useful information, but it can be improved by providing more detail and increased clarity on the installed system; at points the text is confusing. Some of the sentences are very long (even repetitive) but do not provide much clear information; the terms used are not always rigorous. It is expected that this can be improved by careful re-writing based on the following technical and editorial comments.
Line 13 ..using [-insert-] -hybrid galvanic- cathodic protection
L 16 zinc –anode- samples
L 33 provide reference for (ref)
L 40 what is meant by “all this”?
L 43 there is a considerable number of papers on working lives of ICCP system (many more than referred here), but less so on GCP
L 61-63 are repeated in L 74-76
L 65 please explain the essence of hybrid GCP in more detail
L 80 mention 39 piers
L 83 please explain “at the two brackets” does this mean the abutments?
L 111 please be more specific in which areas corrosion developed
L 120 please explain the “Fosroc” technology – is this an ICCP, a GCP or a hybrid system? In the remainder of the paper, this system appears not to be addressed – why?
L 125 please explain in more detail the CPT technology (better called Duogard?): this is the core of the paper! In fact, the design and application to the structures (piers only?) should be detailed here, not in section 4.3. This includes its monitoring system (number and position of MnO2 reference electrodes, RE) and protection criteria (partly described in 3.2).
L 164 report frequency of monitoring, “intense” and “scaled down” are too vague
L 177 – 185 This is confusing: CP quality should be assessed according to the relevant standard, ISO 12696. ASTM C876-15 does not apply to CP ,but to ”free corroding steel”. This suggests that there were RE’s outside the areas of CP; is this correct and if so, where?
L 192 the ISO 12696 criteria are not correctly represented: decay up to 24 h should be 100 mV or more; over more than 24 h should be 150 mV or more
L 195 what is meant by corrosion risk through potentials? The ASTM boundaries do not apply under CP.
L 196 please report in full the decay values of as many piers as possible; a) there is a big difference in 24 h decays of say 80 mV (although strictly not complying) and 20 mV (certainly not complying); b) the assessment of the effectiveness of the (hybrid) GCP system over time relies on such information
L 197 – 206 ASTM does not apply to steel under CP; if this is used to evaluate corrosion outside the areas with CP, please explain this clearly
L 211 Piers 4 and 37 are taken representative for CP – did the decay here comply to the criteria?
L 219- poor English, this should read: First, on a fresh surface, micro-XRF was used to map the total chloride content. Then silver nitrate was sprayed for visual detection of chloride penetration. Finally, the chloride profile was determined in the laboratory according to EN 14629.
L 227 pleas provide title and reference for DNV-RP-B401. How were the anodes cleaned – chemically or mechanically?
L 240 section 4,1,1 please reconsider this and the next paragraph, please explain the background of Fig 2. Are these potentials under CP? On or OFF? Etc.
L 248 It is obvious that installed RE’s only measure local potentials. What information (visual?) suggested that there was corrosion (outside the repaired areas?). From the system description (now in 4.3) it appears that the complete surface of the piers was under CP. If that is correct, how can there be corrosion? Or did the CP system not work properly? Please clarify!
L 264 cores were extracted in repaired areas or in non-repaired areas?
L 269 explain what is meant by “recovered to saturation”.
L 273 “The lowest .. to be 0.6%..” Was this determined on cores from this structure? If correct, please say so (important!). If from literature, provide reference.
There is considerable disagreement in literature about the chloride threshold (CT), even after intense attempts, a.o. by RILEM (see Tang et al., RTLetters 2018). Unless the authors have determined the CT for this structure (see comment above), there is no literature value that can be used with confidence, except a general range, e.g. from fib Bulletin 34 (2006). However the statement by Bertolini et al 2014 is correct: with CP that complies to the criteria, the CT is much higher.
L 287 what chloride extraction is meant here? Removal of chloride contaminated concrete (for the repairs)? Or an effect of the ICCP phase? Please clarify.
L 292 Consider deleting this paragraph; without further documentation (and explanation) it does not provide useful information to the reader. Similarly, delete Table 1 and Figs 6 – 9.
L 315- Please reformulate: “As part of the evaluation 10 anodes were removed from piers 4, 9 and 37. In Figure 10 shows the recovered anodes alongside one of the original
anodes that was preserved for comparison. Table 2 reports the remaining zinc mass percentage.” A question is why anodes were taken from these piers? And did they comply to the CP criteria? Please report results for all 10 anodes; the scatter (dispersion) is important. how does this compare to Sergi’s data (and what were those data?)?
L 328- Why mention realkalization? Carbonation has not reached the reinforcement. Do the authors mean repassivation? What signs of corrosion were detected?
L 336 (polarised) corrosion potentials under CP should be more negative than say – 350 CSE. Or was this outside the area with CP (again, clarify). The following text suggests it was in the CP area.
L 339 Please explain the procedure of applying impressed current. Was the impressed current measured? Applying 12 V does not say anything..
L 341 suggests something interesting: that the zinc anodes were activated by the impressed, as if they had been passivated. Passivation of zinc in concrete over time happens quite easily. This also raises the question which current x time (charge) the anodes had passed until they had lost 15% of their mass (Table 2).
L 344-348 This paragraph does not seem to be correct. In ISO 12696 there is no such limit as – 500 to -750 mV; hydrogen evolution (and embrittlement) can be avoided under ICCP by keeping the potential more positive than -900 mV.
L 349 Fig 4 requires clarification, it is very hard to understand. Please reconsider how to present the data (before/after).
L 353 reports some currents, which should be reported before as general performance indications of the system.
L 356 In this reviewers opinion, reduced currents after the impressed current phase do not indicate a lower (galvanic) current requirement of the steel, but a smaller potential difference between the anodes (typically -1000 mV) and the steel that has a more negative potential due to the impressed current phase.
L 359 should be in a Recommendations section; replace transmissivity by conductivity or resistivity
L 365 a correlation to what?
L 373 Residual life estimation –of the GCP system-
L 375 “generally” – in which reference? By recommendation of the supplier?
This section described the design of the CP system; it should be provide much earlier in the paper.
L 383 is there a standard spacing for Duogard, and if so, what is it?
L 402 at 250 mm; L 404 at 200 mm L 407 pier diameter is 4 m. Please note, 0.3 m2steel/m2concrete is a very low value compared to other infrastructure
L 427 CP of the piers (not repair)
L 432 is there a reference for these 85% and 85%?
L 435 can the assumption of 5% be supported by evidence, eg. current measurement?
L 445 The calculation is based on assumed current output. BTW, Holmes et al. is not in ref [23]. Lifetime calculation should be based on current measurement during GCP (plus the ICCP phase), even if it is necessary to make assumptions, e.g. about temporal variation.
L 460 The correct term is “Electrical charge” (current x time) instead of load; current measurement data is missing in 4.1.3
L 464 For Table 5, please explain how “estimated consumption” and “measured consumption” were calculated.
L467 – 484 Please indicate that these considerations are based on important assumptions. One is that the aggressiveness remains constant; which is not very realistic considering that chlorides will continue to penetrate, and carbonation may over time increase, also increasing current demand. The second is that more interventions with temporary impressed current may be needed, which reduce the amount of zinc considerably for each application. A final limitation is that from the present data it cannot be seen how well the system performed in terms of corrosion protection (reporting decay data may help here); so ultimately the calculation may be correct in that the amount of zinc will last another 50 – 60 years, but if corrosion re-appears due to insufficient cathodic protection, the structure will lose steel and will develop damage, requiring further repairs.
L 500 “no significant damage was found in protected sections” this is interesting and should have been reported earlier in the paper.
L 508 re-application of temporary impressed current treatment could very well be based on decreasing decay values (below a certain limit); what was the reported re-application based on?
L 509- see comments above
L 571 ref 19 please indicate which journal etc.
Comments on the Quality of English LanguageCan be improved; some sentences or paragraphs need re-writing (indicated)
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsAssessment of the residual life of the repaired Arousa Bridge
Abstract
Results to be added and value added to researchers and practitioners by assessing the effectiveness of the repair measures.
Criticize the literature not just presenting their findings in sections 1 and 2.
Figure2 Repair made on the deck around the pier 38 during the 2021 repair: needs labels of repair works and discuss this labels intext. Also in figure 3 highlight on the figure and discuss in details the Signs of corrosion initiation in pier 1.
Pictures in figure 7 and figure 8 needs realignment.
1. Main Question Addressed by the Research
The primary question is:
How effective is the cathodic protection system installed on the Arousa Bridge in prolonging its service life, particularly following repairs made in 2011?
The study examines the residual life of this system through empirical evaluation of corrosion, chloride ingress, and anode consumption over a 12-year period.
2. Topic Originality and Relevance
Originality: The paper is original in its empirical focus on long-term cathodic protection performance, especially in a real-world infrastructure setting.
Relevance: Highly relevant to civil engineering, infrastructure maintenance, and corrosion prevention.
Gap Addressed: The study fills a notable gap concerning the long-term empirical evaluation of hybrid cathodic protection systems in marine environments. Such longitudinal studies are rare but essential.
3. Contribution to Subject Area
Compared with other literature, this paper:
Provides a quantitative assessment of zinc anode performance over 12 years.
Demonstrates the practical value of hybrid cathodic protection for major infrastructure.
Enhances our understanding of residual life prediction methods, combining core sampling, chloride profiling, and impressed current analysis.
4. Methodology – Evaluation and Suggestions
Strengths:
Real-world data from a long service timeline.
Use of core extraction, chloride mapping, and electrochemical analysis.
Adherence to recognized standards (ISO 12696, ASTM C876).
Improvements Needed:
Clarify sampling rationale: Why were only 3 piers selected for core extraction? Justify the representativeness.
Statistical rigor: More formal analysis of uncertainty or error margins in measurements would strengthen reliability.
Limitations: Include discussion of methodological limitations (e.g., limited access, sensor degradation, or environmental variability).
5. Consistency of Conclusions with Evidence
Yes, the conclusions are consistent and well-supported by:
Zinc consumption rates.
Electrochemical potential changes.
Chloride threshold evaluations.
However, the suggestion to standardize re-alkalization protocols would benefit from a broader contextualization—i.e., applicability to other bridges and climates.
6. Appropriateness of References
Excellent use of high-quality and recent literature.
Includes both technical standards and peer-reviewed publications.
Appropriate citations of past research on the same bridge enhance traceability.
7. Tables and Figures
Well-presented and enhance comprehension.
Figures are clear but would benefit from:
Consistent scaling across graphs.
A map of pier locations for spatial context.
Clearer captions for some FRX images (Figures 6–8) to aid non-specialists.
Language Review and Examples
1. Grammar and Sentence Structure
Original: “This works analyses the situation...”
Improved: “This work analyzes the situation...”
Original: “The consumption of zinc anodes installed in the structure was measured...”
Improved: “Zinc anode consumption was measured...”
2. Awkward or Redundant Phrasing
Original: “...the protection capacity as the surface of the anode is covered with the deposits...”
Improved: “...as deposits accumulate on the anode surface, reducing its protection capacity...”
3. Inconsistent Tense or Word Forms
Original: “It can works under impressed current...”
Improved: “It can operate under impressed current...”
4. Articles and Prepositions
Original: “...was applied to the complete bridge as preventive measure.”
Improved: “...was applied to the entire bridge as a preventive measure.”
5. Typographical and Formatting Issues
Inconsistent punctuation (e.g., commas in lists).
Spacing errors (e.g., double spaces after periods).
Equation formatting should be standardized.
6. Clarity and Readability Enhancements
Use of shorter sentences would improve flow in technical sections.
Headings could benefit from numbering hierarchy (e.g., 4.1.1 instead of nested text only).
7. Suggestions for Overall Language Improvement
Professional copy-editing is strongly recommended.
Streamline and polish scientific tone for an international journal audience.
Suggested Structural Improvements
1. Abstract
Add explicit mention of key results and numerical findings.
Include a brief note on methods used.
2. Introduction
Contextualize the bridge in regional infrastructure importance.
Provide a clearer statement of objectives and research questions.
- Literature Review
Consider making this a distinct section.
More comparative insight on hybrid systems in other geographies.
4. Methodology
Clearly separate inspection protocol, core sampling, and zinc analysis.
5. Results and Analysis
Excellent depth, but results and discussion could be split more distinctly.
6. Discussion
Explore cost-benefit implications of findings for infrastructure policy.
7. Conclusion
Strengthen final summary by highlighting:
Broader applicability.
Recommendations for maintenance protocols.
Strengths Summary
Technically robust and field-relevant.
Demonstrates long-term monitoring best practices.
Strong documentation and application of standards.
Final Thoughts
Paper Originality:
Good
Contribution to Scholarship:
Significant in infrastructure durability and cathodic protection fields
Structure and Clarity:
Average – could be improved by clearer sectioning and language editing
Logical Coherence:
good, with well-reasoned conclusions
Methodological Soundness:
Yes, but more transparency and statistical rigor are encouraged
Engagement with Recent Literature:
Strong and comprehensive
Comments on the Quality of English Language
Language Review and Examples
1. Grammar and Sentence Structure
Original: “This works analyses the situation...”
Improved: “This work analyzes the situation...”
Original: “The consumption of zinc anodes installed in the structure was measured...”
Improved: “Zinc anode consumption was measured...”
2. Awkward or Redundant Phrasing
Original: “...the protection capacity as the surface of the anode is covered with the deposits...”
Improved: “...as deposits accumulate on the anode surface, reducing its protection capacity...”
3. Inconsistent Tense or Word Forms
Original: “It can works under impressed current...”
Improved: “It can operate under impressed current...”
4. Articles and Prepositions
Original: “...was applied to the complete bridge as preventive measure.”
Improved: “...was applied to the entire bridge as a preventive measure.”
5. Typographical and Formatting Issues
Inconsistent punctuation (e.g., commas in lists).
Spacing errors (e.g., double spaces after periods).
Equation formatting should be standardized.
6. Clarity and Readability Enhancements
Use of shorter sentences would improve flow in technical sections.
Headings could benefit from numbering hierarchy (e.g., 4.1.1 instead of nested text only).
7. Suggestions for Overall Language Improvement
Professional copy-editing is strongly recommended.
Streamline and polish scientific tone for an international journal audience.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for Authors1. The key words are the refinement of the abstract, usually no more than five.
2. Although the introduction mentions the corrosion issue, it fails to adequately specify the challenges posed by the marine environment. It is recommended to supplement with detailed information about the specific corrosion challenges in this area and how these challenges affect the selection of repair technologies.
3. The article covers a real-world long-span bridge and includes detailed historical maintenance records, providing valuable insights for the long-term monitoring of cathodic protection.
4. The research methods for core sampling are not sufficiently clear, and there is an inadequate explanation of why specific areas were chosen for sampling. It is recommended to clearly state the reasons for selecting the core sampling locations.
5. There is a problem with duplicate image labels. Please find the attachment.
6. The results regarding chloride ion penetration and carbonation are described, but there is no in-depth discussion on how these results impact long-term durability.
7. The horizontal and vertical coordinates of the figure 5 are missing.
8. The photos of the actual corrosion morphology have no scales and the sizes of photos are inconsistent so that they cannot be compared. It is suggested to supplement the scales in figure 6/7/8/10.
9. The text proposes a suggestion for periodic re-alkalization and recommends providing a brief economic analysis to support the re-alkalization strategy.
10. The units in the title columns of Table 3 and Table 4 are not accurate enough. The title of Table 5 should be on the same page as the table.
11. The references are too outdated. It is suggested to add literature from the past three years.
(For specific modifications to this content, please find the attachment.)
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThanks to the authors for absorbing review comments. The manuscript can now be accepted for publication.
