## 1 Introduction  
Process plants are one of the topics that many researchers have devoted their time to exploring, with process plants covering a wide range of industries, such as petrochemicals, oil and gas, power plants, and food production. These studies address vital areas, such as the design, fabrication, and material selection of plant equipment, as well as construction procedures, testing requirements, safe operating practices, maintenance strategies, and overall operational efficiency [1, 2, 3, 4, 5].  
This review explores the potential application of phased array corrosion mapping (PACM) during plant operations to restrain the total turnaround maintenance (TAM) duration. The goal of redistributing the inspection workload during TAM and ensuring the availability of spare parts prior to scheduled maintenance is to reduce downtime. This review was structured into two categories to provide a holistic perspective. The first category elucidates the diverse traditional maintenance strategies prevalent in process plants, thereby enhancing the understanding of maintenance terminology. This section also encapsulates the challenges researchers face in TAM and introduces diverse methodologies for enhancing TAM systems. Techniques, such as assessment tools for optimization [6; 7], questionnaire surveys [8; 9], software aid development, and Risk-based Inspection methods [10; 11], have emerged as effective approaches in this context.  
The second focus area of the review deals with PACM, which is currently applied in plant inspection and maintenance. It also addressed the advantages and limitations of the proposed method.  
An important insight from the reviewed literature is that researchers mainly share the common goal of minimizing TAM duration and extending TAM intervals, thus reducing TAM costs. A common solution that has attracted considerable attention is strategically shifting the TAM activity to on-stream inspections.  
The PACM is gaining prominence because it can swiftly detect localized corrosion and cover larger scan areas in less time. However, it is challenging to apply this technique during on-stream inspections where elevated temperatures often exceed the recommended ultrasonic testing (UT) temperature limit of 52 \({}^{\circ}\)C [12]. Yet, successful articles related to PACM applications exist and have been successfully applied in various industries, such as oil and gas, power generation, and marine, to detect and monitor corrosion growth without shutdown. For example, in the oil and gas industry, PACM has been used to inspect pipelines and storage tanks, enabling operators to identify and address corrosion issues before they lead to failures or leaks [13; 14; 15]. Most of these applications have been conducted at ambient temperatures. However, there are some exceptions, such as [PERSON] et al. [16], who introduced the use of a dual linear probe to conduct PACM experiments at temperatures of up to 150 \({}^{\circ}\)C.  
This review underlies the growing inclination toward integrating on-stream inspections with normal plant operations to curtail the overall TAM duration. The efficacy of PACM in swiftly detecting localized corrosion reinforces its potential and underscores the need for further investigation.  
Future research aims to evaluate phased array corrosion mapping on piping typically joined by multi-bolt systems [17; 18; 19] that can perform inspection during the plant's operation (on-stream) up to 400 \({}^{\circ}\)C to effectively detect general and localized corrosion in the most common materials. Furthermore, it reduces TAM duration and extends TAM interval.