Some years ago we made corrosion tests on cut leads that where associated with the solder fillet being separated from the lead. We had the specimen in H2S / SO2 atmosphere, 100% humidity for 2 months. The result was, that we found corrosion on the cut end of the leads if they where made of Alloy42. Copper leads did corrode but just on the surface. The whole rest of the solder joints didn't show a problem.
Conformal coatings do not solve the corrosion problem if there is any. All polymers are permeable to water. If the coating doesn't adhere perfectly to the substrate a local microclimate will form with 100% humidity. Even condensation can occur ( same as blisters under the colour of a car ) if some hygroscopic material is present. This will make corrosion more likely than in fresh ( or not so fresh ) air.
I suggest you check whether the fracture is only in the filet or running into the through hole. I assume the crack will be limited to the filet region and is only a cosmetic problem.

Best regards

Guenter

Guenter Grossmann
Swiss Federal Institute for Materials Testing and Research EMPA
Centre for Reliability
8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :      xx41 1823 4054
mail:     [log in to unmask]

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