# NDT Methods Comparison Chart: Which Test Finds What > Source: https://netray.co/tools/ndt-methods-selection-reference > Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems. > Section: Free Tools ## Short answer Searchable comparison of common NDT methods covering the defects each finds, where it looks, and its main limitations. ## Category quality ## Industry Aerospace and Manufacturing ## Audience - Quality engineer - NDT technician - Supplier quality ## Tool **Kind:** worksheet **Mode:** reference **Columns:** #### Method **Key:** method **Type:** text #### Abbrev. **Key:** abbr **Type:** text #### Typically finds **Key:** finds **Type:** text #### Reach **Key:** reach **Type:** text #### Main limitations **Key:** limits **Type:** text **Rows:** **Method:** Visual testing **Abbr:** VT **Finds:** Surface discontinuities, weld profile, corrosion, misalignment **Reach:** Surface **Limits:** Depends on lighting, access and inspector skill **Method:** Liquid penetrant testing **Abbr:** PT **Finds:** Surface breaking cracks, laps, porosity **Reach:** Surface breaking only **Limits:** Needs clean, non porous surface; smeared metal can hide cracks **Method:** Magnetic particle testing **Abbr:** MT **Finds:** Surface and near surface cracks and laps **Reach:** Surface and slightly subsurface **Limits:** Ferromagnetic materials only; field direction matters **Method:** Ultrasonic testing **Abbr:** UT **Finds:** Internal flaws, laminations, thickness loss, weld defects **Reach:** Volumetric **Limits:** Needs couplant and skilled interpretation; rough or complex geometry is hard **Method:** Phased array ultrasonic testing **Abbr:** PAUT **Finds:** Weld flaws, corrosion mapping, composite defects **Reach:** Volumetric **Limits:** Equipment cost and procedure development effort **Method:** Radiographic testing **Abbr:** RT **Finds:** Porosity, inclusions, voids, lack of fusion, wall thickness **Reach:** Volumetric **Limits:** Radiation safety controls; tight planar cracks may be missed if misaligned **Method:** Computed tomography **Abbr:** CT **Finds:** 3D internal voids, porosity, assembly condition **Reach:** Volumetric **Limits:** Part size and density limits; high cost per part **Method:** Eddy current testing **Abbr:** ET **Finds:** Surface and near surface cracks, conductivity, coating thickness, tube wall loss **Reach:** Surface and near surface **Limits:** Conductive materials only; limited depth **Method:** Leak testing **Abbr:** LT **Finds:** Leaks in vessels, seals and welds **Reach:** Through wall **Limits:** Method must match required leak rate and medium **Method:** Acoustic emission testing **Abbr:** AE **Finds:** Active crack growth and corrosion in loaded structures **Reach:** Whole structure **Limits:** Needs loading and noise control **Method:** Infrared thermography **Abbr:** IR **Finds:** Delaminations, disbonds, moisture, hot spots **Reach:** Near surface **Limits:** Needs thermal contrast and emissivity control **Method:** Positive material identification **Abbr:** PMI **Finds:** Wrong alloy or grade **Reach:** Surface composition **Limits:** Light elements such as carbon are not read by common XRF units **Notes:** This is a screening guide for method selection. The applicable specification, drawing note or customer flow down decides the method, procedure and acceptance criteria. NDT personnel are usually qualified to a written practice such as ASNT SNT-TC-1A or an equivalent standard. ## Content **Intro:** Choosing between penetrant, magnetic particle, ultrasonic or radiographic testing starts with what you need to find and where it sits in the part. This chart gives a quick side by side so you can have an informed conversation with your NDT supplier. **Sections:** #### How to use the chart **Body:** Search by a defect name, material issue or method. Look at the Reach column first: surface methods cannot find buried flaws, and volumetric methods are usually not the first choice for fine surface cracks. Then check limitations against your material. For example, magnetic particle only works on ferromagnetic alloys, so aluminum or austenitic stainless parts need penetrant or eddy current instead. #### Selecting and specifying NDT **Body:** Most of the time the customer or specification names the method and acceptance class. Where it does not, choose the method for the failure mode you fear most, then write the procedure reference, sample plan and acceptance criteria on the purchase order or inspection plan. Combine methods when needed, such as penetrant on machined surfaces plus ultrasonic on critical weld volumes. **Bullets:** - State the method and the governing standard on the PO - Require certification level of the examiner - Define 100 percent or sample inspection clearly - Ask for written results to be attached to the lot #### Common mistakes **Body:** Treating NDT as a pass or fail stamp without checking the procedure, using penetrant after shot peening or heavy machining that has smeared the surface, and forgetting post inspection cleaning and demagnetizing. Also confirm that the subcontractor holds the right scope of accreditation or customer approval, because many aerospace primes approve NDT sources by process. **Cta:** If NDT results arrive as PDFs from subcontractors, Netray can help tie them to purchase orders and inspection lots in your ERP. **Faq:** #### Which NDT method is best for surface cracks? **Answer:** Liquid penetrant works on most nonporous materials and finds surface breaking cracks. Magnetic particle is faster on ferromagnetic parts and also finds shallow subsurface flaws. Eddy current suits conductive parts and automated scans. #### Why can't magnetic particle testing be used on aluminum? **Answer:** It relies on a magnetic flux leakage pattern that attracts iron particles. Aluminum and austenitic stainless steels are not ferromagnetic, so no usable leakage field forms. Use penetrant or eddy current instead. #### Is radiography better than ultrasonic testing? **Answer:** Neither is better in general. Radiography gives a permanent image and suits volumetric flaws like porosity. Ultrasonic finds planar flaws such as cracks and lack of fusion more reliably and has no radiation hazard. #### Who qualifies NDT personnel? **Answer:** Employers qualify and certify personnel under a written practice based on a standard such as ASNT SNT-TC-1A, ISO 9712 or NAS 410 for aerospace. Customer flow downs may add requirements. ## Search terms NDT methods comparison, liquid penetrant vs magnetic particle, NDT method selection chart, non destructive testing methods table, PT MT UT RT ET differences, which NDT method for cracks, NDT reference chart, eddy current vs ultrasonic --- Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json