I am not a fan of Boshield T-9 for protecting cast iron tops and tools. Looking at the SDS, my interpretation is that it appears to basically be Vaseline (petroleum jelly) and an oil with a bunch of solvents and an emulsifier. It has a small amount (<6%) of sodium sulfonate which inhibits corrosion. I much prefer paste wax for protecting against rust. T-9 does seem to work but it takes a while to dry and I always feel like I need to wipe most of it off while it is still wet. Perhaps it is better for when you live near the ocean?
--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.