I recommend this with caution for two reasons...first, it would be best for me to see a photo of what you are actually describing before recommending a product and secondly, this particular product may or may not be the best for your job. It is very strong and for the most part...permanent! Very difficult to remove once cured. It does, however, stop seam leaks. Can be used under the waterline in marine applications.
3M 5200. 3M use to offer the 4200 which is similar but not so permanent! I couldn't find it anymore.