During material inspection, which test is used to identify the chemical composition of the base metal in a pipe?

The question asks to identify the test used to determine the chemical composition of the base metal in a pipe during material inspection. The image provided shows an "XRF Analyzer" being used on a pipe.

Let's evaluate the given options:

• A. Ultrasonic Testing (UT): This method uses high-frequency sound waves to detect internal flaws, measure thickness, and characterize material properties based on sound wave propagation. It does not identify chemical composition.
• B. Radiographic Testing (RT): This method uses X-rays or gamma rays to detect internal discontinuities like voids, cracks, or inclusions by analyzing the differential absorption of radiation. It does not identify chemical composition.
• C. Positive Material Identification (PMI): This is a non-destructive testing method used to verify the chemical composition of materials. It is crucial for quality control and safety in industries where material grades must be precisely known. Common techniques used for PMI include X-ray Fluorescence (XRF) and Optical Emission Spectrometry (OES). The "XRF Analyzer" shown in the diagram is a device specifically used for PMI.
• D. Magnetic Particle Testing (MT): This method is used to detect surface and near-surface discontinuities in ferromagnetic materials by applying a magnetic field and magnetic particles. It does not identify chemical composition.

Based on the function of each test and the explicit mention of an "XRF Analyzer" in the diagram, Positive Material Identification (PMI) is the correct answer.

The final answer is $\boxed{\text{C}}$