Chloride induced corrosion is the prime reason for the degradation of embedded rebar in reinforced concrete marine structures. The present study experimentally investigates the effectiveness of traditional two-component epoxy (EPX), and moisture-cure polyurethane coatings (MC) applied on the concrete surface in reducing the rate of chloride ingression compared to the conventional concrete with and without mineral admixtures like fly ash and GGBS. Coatings used in the present study are characterized by XRD, EDAX, FEG-SEM, water uptake, adhesion strength and contact angle tests. Rapid chloride migration tests (RCMT) were conducted on concrete with and without coatings. Resistivity offered against the chloride migration monitored during the RCMT test indicated that concrete with MC shown higher resistivity in the initial period and continued to decrease over the test duration at a faster rate, unlike EPX. The non-steady-state migration coefficients of the concrete cured for 28days and coated with MC and EPX coatings were found to be nearly 22% and 48% of that of concrete with SCM cured for 84days respectively. The study is further extended to monitor the corrosion of rebar embedded in coated concrete subjected to corrosion acceleration until the first crack appeared on an uncoated specimen. Variation in current flow, half-cell potentials recorded during the acceleration test and actual mass loss of embedded rebar estimated by gravimetric analysis are presented in this paper. 

Soil-side corrosion of above ground storage tank bottoms is a major challenge for the midstream operators owning tanks farms. In North America most of the above ground storage tanks include active cathodic protection (CP) systems to protect soil-side of the tank bottoms from corrosion. However CP systems could fail leading to unprotected tank bottom and sometime extensive corrosion could occur even with an active CP system in place. In addition a tank without a CP system could experience elevated corrosion including pitting corrosion. Vapor corrosion inhibitors (VCIs) are being promoted as alternative corrosion control measures.A pipeline research council international (PRCI)-sponsored study was conducted to evaluate effectiveness of the VCIs in mitigating corrosion. The study was conducted to determine to determine whether the VCIs are effective in mitigating corrosion to a level comparable to a working CP system for tank bottoms. Extensive amount of laboratory scale testing was conducted and the experimental data were rigorously analyzed. It was found that the VCIs are effective in mitigating corrosion when vendor specific recommended dosages are used but the corrosion rates were not mitigated to the extent specified in NACE SP0193 and NACE SP0169 for demonstrating adequate cathodic protection.

In this study, the effect of Mo, Cu and W contents in stainless steels on both NAC and PTA SCC resistance are investigated. The purpose was to optimize a proprietary version of UNS S34751 (TP347LN) with excellent PTA SCC resistance.

Electrochemical methods were used to evaluate pitting susceptibility of differently heat-treated DSS samples. Results from this study provide further knowledge on the heat treatment effects for the relatively new grades of lean duplex stainless steels.

The effects of three blasting methods utilised for surface preparation upon the behavior of five organic coating systems are investigated. The blasting methods include dry blast cleaning, UHP and UHPAB. It is shown that pull-off strength, pull-off failure mode, and delamination are significantly affected by the surface preparation method. 

The Kentucky Transportation Center (KTC) conducted a study funded by the Kentucky Transportation Cabinet (KYTC) to assess the impact of chlorides on bridge coatings performance. 

Nuclear Regulatory Commission (NRC)Washington DC 20555Copper (Cu) is a candidate waste container material for high-level radioactive waste geologic disposal systems located in the saturated zone because of its thermodynamic stability in anoxic water. However chemical species in the groundwater could change its stability and electrochemical properties especially corrosion resistance. This study investigated the role of chloride (Cl–) in Cu corrosion in solutions containing sulfate (SO42–) and Cl– with residual oxygen (O2) concentrations of about 0.1–0.2 ppb at 20 °C and 50 °C. SO42– concentration was kept constant at 2000 ppm while Cl– concentration was varied from 0 to 1000 10000 and 100000 ppm. Electrochemical methods including corrosion potential (Ecorr) monitoring potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to study the electrochemical properties of Cu affecting corrosion resistance.All the results obtained from different methods consistently demonstrate that Cl– and temperature play significant roles in enhancing corrosion of Cu when O2 concentration is extremely low. Ecorr decreased with increasing Cl− concentration and was lower at 50 °C than at 20 °C. During both forward and reverse potentiodynamic polarization scans Ecorr consistently decreased and the current density increased with increasing Cl− concentration. Tafel slopes from the forward scan regions decreased and the exchange current density increased with increasing Cl− concentration. The EIS data differed in solutions with different Cl− concentration levels and they became more complex at elevated temperatures. A layered film structure was inferred from the EIS data. Polarization resistance derived by fitting to the EIS data was lowest at the highest Cl− concentration which is consistent with increasing corrosion rates with increasing Cl− concentration. The detailed results will be discussed in thepaper.This abstract is an independent product of the CNWRA and does not necessarily reflect the views or regulatory position of NRC. The NRC staff views expressed herein are preliminary and do not constitute a final judgment or determination of the matters addressed or of the acceptability of any licensing action that may be under consideration at NRC.

Aboveground Storage Tanks (AST) degradation is mainly caused by bottoms corrosion. The paper includes a case study, where historical inspection records of more than sixty (60) AST with different hydrocarbon fluid services and bottoms corrosion control systems were reviewed and analyzed.

Alloys are often found to suffer much greater metal-dusting attack under high-pressure conditions compared to ambient-pressure conditions. Ultimately, the resistance of a given alloy to metal dusting depends on the formation of an oxide scale that is impermeable to carbon which, in turn, depends on scale composition and structure. This paper reports the metal-dusting behavior of several Ni-based alloys having relatively high Cr contents (about 30 wt.%) and different controlled minor levels of Fe, Al, and/or Si. Testing was conducted under 20 bar total pressure of a high-carbon-activity gas at 600 °C (1112 °F). The exposed alloys were analyzed by SEM and TEM techniques to evaluate the oxide scales and evidence of carbon ingress. It was found that aluminum is beneficial to improve metal dusting resistance by reacting to form a continuous inner layer of alumina; whereas iron is detrimental to resistance. Mechanistic aspects of the role(s) played by minor elements in affecting metal-dusting resistance are considered.  

Recently several localized corrosion and cracking failures happened to API 5CT Grade C110 tubing in high-density formate completion fluid at high temperature because of the leakage of CO2 and the mechanical damage on the tubing surface. In this paper the hydrochemical simulation software is used to calculate the needed content of pH buffer. The corrosion behavior of C110 tubing is investigated by autoclave scanning electron microscopy (SEM) energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results show that 1% Na2CO3 and 1%NaHCO3 can maintain the pH of formate completion fluid with the mix of 3 MPa CO2 up to 6.35 which means CO2 corrosion restrained effectively. The simulated experiments show that the general corrosion rate of C110 tubing decreases from 0.49 mm/a to 0.24 mm/a and the C110 tubing have little localized corrosion and cracking susceptibility in formate completion fluid when buffered with 1% Na2CO3 and 1%NaHCO3. The results of XRD and SEM-EDS indicate that the pH buffer is helpful to general compact and effective FeCO3 corrosion product film.

High level radioactive waste is stored in 28 double shell tanks (DSTs) at Hanford. The secondary shell rests on a concrete pad that have indentations that provide a path for flow in case there is a leak for detection. It Is known that water can accumulate in the concrete indentations that needs to be pumped out of the pad from time to time. Ultrasonic tests have determined that there is some thinning of the bottom walls of the secondary tank that may have been caused by general and vapor space corrosion (VSC). A set of experiments were established by using a commercially available vapor corrosion inhibitor (VCI) to test its efficacy in mitigating general and VSC corrosion when it is applied at the surface of carbon steel and when is added into the water. Electrical resistance (ER) probes were also utilized to measure VCI efficacy at a level close to the liquid. The paper will present results of the testing and efficacy of VCIs in mitigating the vapor space corrosion of the secondary liner.

Mildly acidic water containing dissolved H2S presents a strong risk in the cracking of mild steels. The main driving force is associated with the ability of H2S to promote hydrogen entry into steel. Lots of studies on H2S cracking mechanisms have been performed for oil and gas applications since it is a huge concern for this industrial sector. Standard test methods have been developed and published as NACE technical methods (e.g. NACE TM0284 and NACE TM0177). Though it is recognized that oxygen pollution should be avoided during H2S cracking tests there is still a lack of experimental data to illustrate the potential impacts of a small oxygen pollution. In standard glass vessels used for the evaluation of steel resistance to H2S cracking appropriate test procedures should allow for the controlling of O2 levels below 50 ppb. However higher values can be reached in the case of poor laboratory practices.In the following study continuous O2 injection at a level corresponding to 500 ppb is applied together with H2S bubbling in the test solutions. This paper will focus on the interactions between oxygen and H2S on electrochemical behavior of unalloyed steel. A test duration of the same order of standard SSC tests is applied. Surface reactions in H2S saturated water with or without oxygen pollution are studied through electrochemical impedance spectroscopy. EIS diagrams showed a strong influence of the highly porous and conductive iron sulfide scale that forms rapidly in H2S environments. This FeS film had to be taken into account in the impedance model in the form of a porous electrode element placed in parallel to the more conventional circuit corresponding to anodic dissolution with adsorbed intermediates already used in the literature for H2S corrosion.The evolution of corrosion rates obtained from impedance analysis was compared to two other independent methods: i/ weight loss measurements and ii/ hydrogen permeation. Without O2 pollution a permeation efficiency of 100% was obtained as expected. Permeation current density was thus found to match precisely with the corrosion current density determined by impedance analysis at different times. Weight-loss measurements also confirmed the validity of impedance analysis. On the other hand when a continuous O2 pollution was added in the system significantly higher corrosion rates were observed associated with test solution acidification. At the same time permeation efficiency was decreased by up to one order of magnitude.