What is a commonly used penetrant in dye penetrant testing?

In dye penetrant testing, the commonly used penetrant is fluorescent dye, which is favored for its ability to enhance visibility under ultraviolet light. This type of dye can easily highlight defects such as cracks, porosity, and other surface discontinuities in various materials. The fluorescent penetrant absorbs UV light and re-emits it in the visible spectrum, allowing for a clearer and more pronounced indication of flaws compared to non-fluorescent options.

Fluorescent dyes are particularly advantageous in dimly lit environments or where enhanced sensitivity is required, as they can be detected even at very low concentrations. This capability makes them a preferred choice in a range of industries, including aerospace, automotive, and manufacturing.

While other types of penetrants, such as red dye, oil-based dye, and water-soluble dye, are also used in certain applications, they do not provide the same level of sensitivity or visibility as fluorescent dyes under the right lighting conditions. Each type of dye has its specific use cases, but fluorescent dyes remain a standard choice due to their effectiveness in detecting very small surface defects.