What Does Edge Failure Mean?
Edge failure is the occurrence of corrosion and other related defects beneath the coated edges of cut-outs, welds, sharp edges, corners, crevices and other surfaces with an angle close to 90 degrees.
Edge failure is basically a design issue that results in inadequate coating protection on the edges mentioned; the coating pulls away from edges as it cures due to surface tension, reducing the thickness compared to the rest of the coated areas.
Edge failure may also be known as edge corrosion or edge defect.
Corrosionpedia Explains Edge Failure
Edge failure is usually design-related but there are corrective measures to make sure that the coating on the edges has the necessary thickness to prevent the development of corrosion.
The basic solution to avoid edge failure is to reduce or eliminate the design features where edge failure is most like to occur. If it’s not possible to design out the potential causes of edge failure, fabrication methods like grinding or chamfering the sharp edges can reduce the probability of thin coating deposits. Other corrective measures are:
- Proper coating application as per industry standards. For instance, if it’s a steel surface, the coating should be according to SSPC-PA 1, Shop, Field, and Maintenance Painting of Steel.
- Using a coating that has the required edge retention properties. According to MIL-PRF-23236C, coatings should have an average of 70% edge retention with no reading below 50%. High-solid coatings typically meet the required film thickness retention on edges.
- Application of “stripe coat” on the edges before or after the regular coating process.
It is important to identify the edges that need corrective measures before surface preparation.