There is no gasket, it just uses sealant, which makes it very difficult to remove. In the UK sump pans regularly rust, particularly at the front where it is most exposed to stones and road dirt. I recently had to replace mine and used a cheap aftermarket sump. This was a big mistake as it would not seal at the end, so I had to replace it with a genuine item (not cheap). If it has rusted I would recommend protecting a new one with waxoil or similar.