Case Study – Use of ZYGLO® ZL-60C for the inspection of automotive suspension systems


February 2017



Our UK customer specialises in automotive component validation; they carry out integrity checks on automotive suspension systems at various points in the component’s life, with the aim of assessing their durability during real use.



Their checks involve a full strip down of the suspension system from the test rig, followed by inspection for surface-breaking defects using a red dye penetrant and solvent-based developer. They were using a wipe technique to remove the excess penetrant, but this method was both messy and time-consuming.



We offered two potential solutions to our customer:

Use our visible red penetrant – SPOTCHECK® SKL-SP2

Using this penetrant would be very similar to what they were currently doing; however, SKL-SP2 is available in bulk format and can be applied by painting it onto the component in a much more controlled way.

Use one of our water-washable fluorescent penetrants – ZYGLO® ZL-19 (Level 1) or ZYGLO® ZL-60C (Level 2)

A Level 1 or Level 2 water-washable fluorescent penetrant would be the most applicable for testing suspension components; a higher level penetrant (commonly used in aerospace applications) is more difficult to remove the excess penetrant. As with SKL-SP2, these products are available in bulk format and can be applied by painting it onto the component in a controlled way. The only difference between these and our our visible penetrant is that a UV lamp is required to identify any defects.

Our customer pereferred to trial our UV fluorescent penetrants, so we also told them about the following associated products:

Solvent-based Developer – SPOTCHECK® SKD-S2

Using a developer helps the inspector to see any surface-breaking defects. Developers typically work by leaving a thin white matt film of inorganic pigments on the component being inspected. This film draws the penetrant back out of any surface-breaking defects and spreads it out on the surface of the part. This action makes it easier to see the defects. Whilst it is not essential to use a developer, unless specified on an internal procedure, there are distinct visibility advantages when using one.

UV lamp – EV6000

Given the customer’s set up and the fact that they preferred a lamp with a wide coverage area, our recommendation was the new EV6000 lamp. This is a mains-operated hand-held unit with the benefits of a strong UV(A) output (4750 – 5000 µW/cm² at 38cm) and a wide beam profile (23cm in diameter >1000 µW/cm² UV(A) intensity).

Our customer was sent a trial pack containing the UV fluorescent penetrants, the solvent-based developer and a UV LED lamp so they could carry out their own evaluations.



During the trials, our customer applied the ZYGLO ZL-19and ZL-60C penetrants using a brush. Removal of the excess penetrant was very easy, even with the Level 1 penetrant; our customer simply poured jugs of water over the components. Going forward, they will look into making a dedicated wash tank for this purpose.

Surface-breaking defects were clearly seen under UV light without application of the developer. Our customer decided that, in most cases, they would look to keep the processing time down by not using the SKD-S2 developer, but will keep a small stock on-hand just in case they need to use this additional step.

The decision was made to go ahead with the Level 2 ZYGLO ZL-60C penetrant. Both this and the developer have now been approved for use.

“We found that using the brush on method using the Magnaflux EMEA UV fluorescent penetrants was a much cleaner and quicker process. Whilst both ZL-19 and ZL-60C gave not dissimilar results, the fact that the Level 2 penetrant was easy to remove makes this our preferred choice.”

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