ABSTRACT
The influence of temperature, pollutant, and pH on the local corrosion rate of insulators installed in industrial, marine, and rural installation sites is investigated based on experimental and statistical investigations. The tensile load test confirms that corroded insulator specimens collected from industrial sites aged more than 10 years represent a minimum fracture load, 19,892 lbs. It was further observed that more than 91.24% and 64.62% corroded insulator specimens suffered from shell break and pin detachment, respectively. The microstructural and XRF analysis reveal that insulator specimens collected from industrial sites (age > 10 years), represented the highest wt% of O (19.2) and lowest wt% of Zn (0.34) among industrial, marine, and rural installation sites. The 3D stationery mechanical simulation reveals that insulator specimens aged > 10 years experienced maximum stress (600 MPa) in the pin-cement interface. Using full two-level factorial designs, temperature, concentration of pollutants, and pH were found significant factors for corrosion rate. The immersion test results further confirm the above-mentioned factors significant for the dissolution behavior of galvanized coating of insulator pin. Following immersion test results, the industrial region shows the highest corrosion rate (5.58-12 µm/year) among all installation sites.
Subject(s)
Alloys , Materials Testing , Alloys/chemistry , Corrosion , TemperatureABSTRACT
Crevice corrosion accounts for 62% of the recorded breakdown of insulators utilized in transmission lines, which may interfere with the reliability of power utilities. To address these challenges, sustainable and resilient slippery lubricant-infused porous surfaces (SLIPS) are developed on insulators to prevent electrochemically/biochemically induced crevice corrosion especially occurring in tropical and coastal environments. The conventional way of developing SLIPS by chemical and physical etching might interfere with the mechanical stability of insulators composed of pin (galvanized steel), cement, and shell (porcelain). The current study proposes a noble concept of developing hierarchical patterned textured surfaces on insulators to fabricate a resilient SLIPS coating without physical/chemical etching. The proposed coating exhibits 99% antiadhesion performance against a mixed culture of bacterial strains, superior hydrophobicity (contact angle: 160°, contact angle hysteresis: 4°), and crevice corrosion resistance performance at elevated temperatures (25-75 °C) and humidity. This study could facilitate a new route for the development of sustainable and highly reliable SLIPS coatings in the future.
ABSTRACT
Due to their great load-bearing capabilities, steel-cement interface structures are commonly employed in construction projects, and power utilities including electric insulators. The service life of the steel-cement interface is always decreasing owing to fracture propagation in the cement helped by steel corrosion. In this paper, a noble crack-resistant solution for steel-cement interfaces utilized in hostile outdoor environments is proposed. A Ce-rich, homogeneous, and thick hydrophobic sealing coating (HSC) is developed on the steel-cement interface after 60 minutes of immersion in a 60 000 ppm CeCl3·7H2O sealing coating solution. The specimens treated with optimized HSC film demonstrate fissure filling, lowest corrosion current (I corr) 2.3 × 10-7 A cm-2, maximum hardness (109 Hv), oxide-jacking resistance (40 years), hydrophobic characteristics, carbonation resistance, and bacterial corrosion resistance, resulting in a crack-free steel-cement interface. This work will pave the way for a new branch of environmentally acceptable coatings for the construction and power industries.
ABSTRACT
Overcoming hardware corrosion for high voltage insulators is a vital issue to prevent the sudden breakdown of insulators. The development of an efficient, economical, and eco-friendly anti-corrosion coating is essential to replace existing carcinogenic and toxic silicone-based coatings used by insulator industries. This article investigates the anticorrosion performance of a novel cerium-based sealing coating for insulator pins installed in highly corrosive (35 µm per year) industrial regions. The coating bath parameters were optimized to improve the self-healing, thermal, crack, and corrosion resistance of the coating. After immersion in a 60 000 ppm CeCl3·7H2O sealing coating bath for 60 minutes, a Ce-rich and dense protective coating (24.4 µm) is formed on the pin surface. The specimens immersed in a 60 000 ppm Ce sealing coating bath for 60 minutes show the lowest I corr. The anticorrosion performance is enhanced by 95% for coated pins than non-coated ones. The electrochemical experiments, macroscopic and microscopic structural analysis confirm the anticorrosion performance of Ce-based sealing coatings for high voltage insulator pins. This work will facilitate a new branch of eco-friendly coatings for insulator and power industries.
ABSTRACT
Pin corrosion is a critical issue that causes premature rupture of high-voltage insulators. The development of efficient, defect-free, thermal resistive, hard, economical and environment-friendly sealing coating system is required to replace the current polymer-based highly toxic coatings for insulators. This study investigates the suitability of noble cerium (Ce)-based sealing coating film for use as an anti-corrosion coating for insulator pins installed in low-pH and highly corrosive sites. The coating bath parameters are optimized for the formation of a high-performance Ce-based protective sealing coating. After immersion in a 60 000 ppm CeCl3.7H2O sealing coating bath for 60 min, a Ce-rich and dense protective coating (24 µm) is formed on the pin surface. The life expectancy of the coated pin is 2.5 times higher than that of the non-coated galvanized pins. Electrochemical experiments and microstructural analysis demonstrate that Ce-based protective layers are suitable for long-term protection of high-voltage insulator pins in low-pH and high-corrosion-rate sites. We believe that this work would pave the way of developing ecofriendly anti-corrosion coatings for electric insulators and power industries.
ABSTRACT
Suspension type porcelain insulators used in overhead transmission lines comprise metal, ceramic, and cement. The deterioration of cement can lead to mechanical separation. For the degradation analysis, varied sizes of pores ranging from a few µm (capillary pores) to tens to hundreds of mm (detectable by naked eyes) were considered. Cracks that were hard to view with naked eyes were identified by staining with a fuchsine solution. The hydrogen ion concentration and pH value indicate the extent to which the cement is deteriorated. The longer the cement is used, the lower its pH value. High mechanical strength is considered an important advantage of porcelain insulators, and it may decline, if the cement is used for a longer period of time. Water ingress may also occur, resulting in expansion, due to the rehydration of the cement. The process and mechanism of expansion of cement, due to infiltration of water were described. As a method of analysis, a universal indicator was employed to evaluate the pH changes in cement. It was observed that the pH value was 12-13 for new products. However, for products that were used for 52 years, the pH value was under 7, which indicated an acidic tendency, due to deterioration.