Antonio..... I have a perfect tank on my K7. The bottom, back corner, left side had pinholes in the bottom seam, under the chrome trim. I guess water had collected there for years. Other than that, the tank was really clean inside. I brewed up some Caswell Tank Sealer and used a funnel and hose to pour 1/4 pint down in that corner. Stood it on end, moving it side to side every few minutes for 1/2 hour. Basically sealed over just the back corner. Can’t be seen, and still holding, 10 years later. I sealed the outside with tape, before starting.... you should try and save that tank!