Hi Bowhunter13,
Try cleaning the marks off with Silvo, Brasso, Stainless Steel cleaner or any other type of Metal Cleaner/polish. Second choice the Cream Cleaners from the supermarket. I say that because the metal cleaners are less abrasive than kitchen cream cleaners and it’s the marks left behind by Titanium you need to remove
They are all strong enough to remove the marks off porcelain without damaging the surface. These products are also perfect for removing rust stains in the bathrooms as well.
As always try a small area first to make sure you are happy with the results. I personally use these types of products in my bathroom and never had any damage done to my tiles. Hope this helps you out.
Regards from Noelene