What is a key difference between nonwater-washable and water-washable penetrants?

The key difference between nonwater-washable and water-washable penetrants lies in the composition and functionality of water-washable penetrants, which include an emulsifier. The presence of an emulsifier in water-washable penetrants allows for the agent to be easily rinsed off with water after inspection, effectively removing excess penetrant while allowing for efficient surface evaluation. This characteristic makes them suitable for applications where post-inspection cleaning is necessary without the use of solvents.

In contrast, nonwater-washable penetrants do not contain emulsifiers, which means they require specific solvents for cleaning off the excess penetrant, making them less convenient in certain environments. Understanding this distinction is crucial when choosing the appropriate penetrant for a particular inspection process, as it affects cleanliness, surface integrity, and the overall effectiveness of the nondestructive testing method used.