## 1 Introduction  
Grounding devices are an essential part of a transmission tower. In the event of a transmission system fault or lightning strike, they allow rapid discharge of fault current to protect control equipment from damage and to ensure the safety of personnel. A transmission tower grounding device generally comprises grounding leads and electrodes. Q235 steel and galvanized flat steel are usually selected as the transmission tower grounding device materials. Because the grounding flat steel service must spend a long time buried deep underground, the water in the soil, inorganic salts, microorganisms, and a small amount of air [1] gradually erode the grounding flat steel, resulting in local corrosion, rust, or even breakage. When the grounding equipment succumbs to corrosion and becomes dysfunctional, the effective grounding area inevitably shrinks, causing a gradual decline in conductivity and increased resistance; this leads to a hazardous situation where the grounding network fails to discharge current effectively, resulting in line tripping and potentially triggering large-scale power outages [2]. Therefore, regular inspection of grounding flat steel corrosion is essential for the safe and reliable operation of the transmission system [3]. However, the conventional method of investigating through excavation is laborious and inefficient., and limitations exist for electromagnetic field-based analysis, the network node method, and electrochemical analysis. As a result, the utilization of a diverse range of non-destructive testing (NDT) techniques, including ultrasonic flaw detection, non-magnetic powder flaw detection, radiographic flaw detection, eddy current flaw detection, and penetrant flaw detection, is increasingly gaining popularity [4; 5; 6]. Conventional ultrasonic inspection techniques rely on piezoelectric ultrasonic transducers to generate ultrasound waves. However, as outlined in the references [7; 8], these techniques have limitations; to ensure adequate transmission of sound intensity at the detection surface during inspections, it is often necessary to utilize a coupling medium between the specimen and the transducer. On the contrary, electromagnetic ultrasound has emerged as a prominent non-destructive testing method and has become an essential detection tool [9]. This technique utilizes electromagnetic ultrasound transducers to produce various types of ultrasound, allowing for non-contact detection and high efficiency [10]. It is a popular choice for inspecting engineering structures such as plates and tubes because it can quickly detect over large areas and long distances [11; 12; 13; 14; 15; 16]. Numerous scholars have delved into the study of electromagnetic ultrasonic inspection technology. [PERSON] et al. studied using electromagnetic ultrasonic non-destructive inspection models to detect cracks in L-shaped aluminum plates. Their research analyzed the distribution characteristics of the electromagnetic ultrasonic transducer field and the influence of different parameters on crack detection [17]. [PERSON] et al. discussed steel corrosion damage detection in difficult-to-reach areas using the beat phenomenon of pseudo-Rayleigh waves at the high frequency-thickness product [18]. [PERSON] et al. proposed a non-contact, in situ, and non-destructive corrosion monitoring methodology for submerged plates using ultrasonic guided waves, using high-frequency guided ultrasonic waves propagating along the structure to achieve non-destructive detection and monitor corrosion damage in hard-to-reach areas [19]. [PERSON] et al. discussed a reference-free guided wave-based corrosion detection algorithm that estimates steel strands cross-section loss using dispersion curves, continuous wavelet transform, and wave velocity [20]. [PERSON] et al. discussed the ability to quantify corrosion damage based on fundamental longitudinal wave mode L(0,1) in steel-reinforced mortar specimens by tracking changes in waveform energy [21].