1.dye testing – staining surfaces with fluorescent liquid, which shows up flaws under ultraviolet lighting
2.magnetic particle testing – applying magnetic particles to magnetized materials, so they line up along cracks and defects (often combined with dye testing)
3.radiographic testing – using X-rays to find internal faults ultrasonic testing – firing high frequency sound pulses into materials and analysing the differences in the reflected signals
ASNT NDT Level 2. Certificate of all the  methods. must be  1-2 years of experience.