Accelerated Corrosion Tests in Quality Labels for Powder Coatings on Galvanized Steel—Comparison of Requirements and Experimental Evaluation

Powder coatings are widely applied for corrosion protection of steel, aluminum, and hot dip galvanized steel in a variety of corrosive environments. Powder coatings are subjected to a number of strict laboratory tests to determine their mechanical properties, corrosion resistance, and color stability. Among European quality certificates for powder coatings applied to galvanized steel, the most commonly recognized are GSB-ST and Qualisteelcoat certificates, which also refer to the EN 13438 standard. Certificates of quality for powder coatings are constantly updated according to the latest research results and experience of specialists operating in the field of corrosion protection. This paper presents an experimental evaluation of how the required length of selected accelerated corrosion tests can affect the final assessment of powder coatings. On the example of two powder painting systems: polyester as well as based on epoxy and polyester resins, the paper presents the influence of the time of accelerated corrosion tests: ISO 6270, ISO 9227 (Neutral Salt Spray and Acetic Acid Salt Spray), and ISO 3231 on the protective properties of the coatings. The results of damage assessment according to ISO 4628 have been correlated with the requirements of particular quality specifications. Additionally, based on FTIR (Fourier Transform Infrared Spectroscopy) and EIS (Electrochemical Impedance Spectroscopy) analyses, the influence of the applied corrosion tests on the degradation degree of the coatings studied has been presented. The paper aims to present a tests for those powder coating systems applied to facilities for which the main requirement is corrosion resistance rather than aesthetics.

Synergistic Inhibition Effect of Chitosan and L-Cysteine for the Protection of Copper-Based Alloys against Atmospheric Chloride-Induced Indoor Corrosion

The protection of metals from atmospheric corrosion is a task of primary importance for many applications and many different products have been used, sometimes being toxic and harmful for health and the environment. In order to overcome drawbacks due to toxicity of the corrosion inhibitors and harmful organic solvents and to ensure long-lasting protection, new organic compounds have been proposed and their corrosion inhibition properties have been investigated. In this work, we describe the use of a new environment-friendly anticorrosive coating that takes advantage of the synergism between an eco-friendly bio-polymer matrix and an amino acid. The corrosion inhibition of a largely used Copper-based (Cu-based) alloy against the chloride-induced indoor atmospheric attack was studied using chitosan (CH) as a biopolymer and l-Cysteine (Cy) as an amino acid. To evaluate the protective efficacy of the coatings, tailored accelerated corrosion tests were carried out on bare and coated Cu-based alloys, further, the nature of the protective film formed on the Cu-based alloy surface was analyzed by Fourier-transformed infrared spectroscopy (FTIR) while the surface modifications due to the corrosion treatments were investigated by optical microscopy (OM). The evaluation tests reveal that the Chitosan/l-Cysteine (CH/Cy) coatings exhibit good anti-corrosion properties against chloride attack whose efficiency increases with a minimum amount of Cy of 0.25 mg/mL.

Potential of Tomato Pomace Extract as a Multifunction Inhibitor Corrosion of Mild Steel

The aim of this paper is to investigate tomato pomace extract (TPE) as multifunctional “green” vapor phase corrosion inhibitor for prevention of the atmospheric corrosion of mild steel and as corrosion inhibitor in neutral media of 0.5 M NaCl solution. The chemical profile of the TPE was analysed using gas chromatography mass spectrometry (GC-MS) and high performance liquid chromatography analysis (HPLC-DAD-MS). The major volatile constituents identified in tomato pomace extract were alcohols (12.5 %), fatty acids (23.78 %), aldehydes (41.6 %), ketones (8.65 %), and terpenoids (9.11 %). The predominant semi-volatile and high molecular weight chemical components in tomato pomace extract were phenolic acids and flavanols. The corrosion protection properties of the TPE as multifunctional corrosion inhibitor were studied using of accelerated corrosion tests (weight loss method) and electrochemical methods (polarization curves and linear polarization technique (LPR)). The mechanism of steel inhibition by TPE formulations was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations. The analysis confirmed that the growth of inhibitory properties is prolonged and corrosion rate is reduced after 40–48 h of exposure. Quantum-chemical calculations were used to predict the adsorption/inhibition properties of some of the main compounds of the extract.

Corrosion Resistance Of High-Performance Composite Beams

The research concentrated on the corrosion resistance of reinforced self-consolidating concrete (SCC), lightweight SCC (LWSCC), fiber reinforced LWSCC (FRLWSCC), Engineered cementitious composite (ECC) and composite (ECC-SCC/LWSCC) beams. The performance of corroded beams were analyzed based on current measurements, half-cell potential readings, crack pattern/width, rebar mass loss and diameter reduction from accelerated corrosion tests. Corroded and their companion uncorroded beams were tested to failure under four-point loading to evaluate load-deflection response, crack pattern, 1st flexure/diagonal cracking load, failure load and failure modes. Composite beams with higher ECC layer thickness exhibited superior corrosion resistance than their lower thickness counterparts and full depth SCC or LWSCC counterparts as well as performance of beams with ECC wrap was better than those with layer. Overall, ECC beams can be a superior alternative of their conventional counterparts and ECC can be used as layer or wrapping in conventional/LWSCC beams to enhance corrosion resistance and structural performance

Corrosion Resistance Of High-Performance Composite Beams

The research concentrated on the corrosion resistance of reinforced self-consolidating concrete (SCC), lightweight SCC (LWSCC), fiber reinforced LWSCC (FRLWSCC), Engineered cementitious composite (ECC) and composite (ECC-SCC/LWSCC) beams. The performance of corroded beams were analyzed based on current measurements, half-cell potential readings, crack pattern/width, rebar mass loss and diameter reduction from accelerated corrosion tests. Corroded and their companion uncorroded beams were tested to failure under four-point loading to evaluate load-deflection response, crack pattern, 1st flexure/diagonal cracking load, failure load and failure modes. Composite beams with higher ECC layer thickness exhibited superior corrosion resistance than their lower thickness counterparts and full depth SCC or LWSCC counterparts as well as performance of beams with ECC wrap was better than those with layer. Overall, ECC beams can be a superior alternative of their conventional counterparts and ECC can be used as layer or wrapping in conventional/LWSCC beams to enhance corrosion resistance and structural performance

Probabilistic Assessment of the Safety of Main Cables for Long-Span Suspension Bridges considering Corrosion Effects

This paper presents a reliability analysis to assess the safety of corroded main cables of a long-span suspension bridge. A multiscale probability model was established for the resistance of the main cables considering the length effect and the Daniels effect. Corrosion effects were considered in the wire scale by relating the test results from accelerated corrosion tests to the corrosion stages and in the cable scale by adopting a corrosion stage distribution of the main cable section in NCHRP Report 534. The load effects of temperature, wind load, and traffic load were obtained by solving a finite element model with inputs from in-service monitoring data. The so-obtained reliability index of the main cables reduces significantly after operation for over 50 years and falls below the design target value due to corrosion effects on the mechanical properties of the steel wire. Multiple measures should be taken to delay the corrosion effects and ensure the safety of the main cables in the design service life.

OPPORTUNITIES TO INCREASE THE CORROSION RESISTANCE OF BUILDING STRUCTURES OPERATING IN AGGRESSIVE PRODUCTION ENVIRONMENTS

This paper presents the results of a study of the corrosion resistance of building structures OF NLMK's CCPP and CDP. It was found that the average percentage of damage is 8.69%, and the areas with high humidity and gas emissions have the greatest corrosion wear of elements. Using a mathematical model of corrosion for zinc and steel, their expected corrosion losses are calculated. It is shown that the greatest mass loss is observed in areas with a concentration of hydrogen chloride above the background value. The results of accelerated corrosion tests of a zinc coating with a crystallite size from 0.6 to 3.5 microns showed that reducing the crystallite size to 0.6 microns reduces the corrosion rate by 2 times, which should increase the service life of the structure by 1.5-2 times compared to traditional materials.

Design and Fabrication of New High Entropy Alloys for Evaluating Titanium Replacements in Additive Manufacturing

High entropy alloys (HEAs) were prepared using the powder bed fusion (PBF) technique. Among titanium free alloys AlCoCrFeNiMn, CoCr1.3FeMnNi0.7, AlCoCrFeNi1.3, and AlCoCr1.3FeNi1.3 have been further investigated. A cost comparison was done for these four alloys as well as the titanium-based alloys AlCoCrFeNiTi and AlCo0.8CrFeNiTi. Such a comparison was done in order to evaluate the performance of the titanium-free alloys as the estimated cost of these will be less than for Ti-based HEAs. Hence, we have chosen four titanium free alloys and two titanium-based alloys for further processing. All these alloys were fabricated and subsequently characterized for phase, purity and performance. Scanning electron microscopy-based images were captured for microstructure characterization. EIS-based tests and potentiodynamic scans were performed to evaluate corrosion current. Hardness tests were performed for mechanical properties evaluation. Additional testing using factorial design tests was performed to evaluate the effects of various parameters to create better PBF-based HEA samples. EBSD tests, accelerated corrosion tests (mass loss), chemical analysis after degradation, microstructure analysis before and after degradation, and mechanical property comparison for finalized samples and other similar tests were executed. The details about all these HEAs and subsequent laser processing as well as behavior of these HEAs have been included in this study. It has been observed that some of the selected alloys exhibit good performance compared to Ti-based alloys, especially with respect to improvements in elastic constant and hardness relative to commercially pure Ti.