Dave, May I suggest using Spot Check by Magnaflux on them. Used by welders to check for cracks. Comes with 3 cans, one is a cleaner, the other a dye (red) and the other can a developer (white). Wipes off with no problem. After you spray on the dye, let sit, and then wipe as clean as you can get it, use a tooth brush near the rib area so as not to leave any dye along seam. Then spray on developer, thin film, let dry. When dry if any cracks are present, they show up as a red line.
Magnaflux company out of Chicago. Find it on eBay, or at a local welding supply.
Good luck.
Last edited by JDW; 12/28/06 08:28 AM.