I need help cleaning off what looks like gray scale on my white vinyl porch railings. There is also black stains where the plastic caps to attach the rails to the post are located. This scale can't be scraped off with a fingernail. The brick house was built in 1950, but the rails were added 6 yrs ago. I don't believe they were ever cleaned. I tried every cleaner in my house and nothing worked. Bar Keepers Friend removed it in a small patch, and it looks shiny, but I am afraid it will scratch. I also want to preserve the flowers I planted around the porch. Have you had the same problem, and if so, what did you use?