Uniform and local degradation of epoxy-based powder coatings: Salt transport and accelerated exposure analysis
Bibliographic record
Abstract
The barrier performance of epoxy-based powder coatings for pipelines was evaluated through salt transport measurements through free-standing coating films and via cyclic testing of coated steel panels. The permeability of salt through the free-standing coating films was measured using reverse osmosis techniques under hydraulic pressures relevant to industrial use. These tests showed that fusion bonded epoxy (FBE) and high-performance powder coating (HPPC) have low salt permeability. Accelerated exposure tests were then conducted on the coated steel panels, subjecting them to humidified environments, ultraviolet (UV) light, and salt/fog conditions, all in accordance with ASTM D5894. Some of the exposure conditions (e.g., intensity of UV light and humidity) were modified to examine the impact of each parameter on the relative performance of these coating systems. The reversibility of the coating properties was characterized by a thermal cycling protocol and adhesion performance analysis. Alternative exposure to dry- and wet-cycles (at 60°C and 50°C, respectively), salt/fog conditions and UV light results in irreversible damage to the coatings as early as two weeks in. However, coated panels exposed to a lower UV intensity (one tenth of the value defined by the standard) showed minimal degradation of FBE, meaning that the most critical parameter was the UV radiation exposure. For one 336-h ageing sequence under UV exposure, the HPPC exhibited superior performance compared to FBE. More importantly, our extended exposure sequences showed that while the FBE coating structure undergoes a slow ablation process, indicating significant surface damage, it still retains its effectiveness as a barrier. However, the osmotic pressures around coated pipes and the pre-existing, unavoidable, porosity throughout the coating thickness can facilitate local through-thickness pinholes, which could potentially serve as areas susceptible to cathodic disbondment.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".