Removing rust or brown spots on inside trailor wings?

[ladywendolyn]

Inside the wings of our shamrock 21 ft camper there are dark brown spots.
They are not on the outside. I do not know if they are rust or some other thing, but I am wondering if anyone else has this issue and if anyone knows how to remove them. Either with a product I can buy or with a home remedy.
Thanks

[milzat]

Wings ??

[ladywendolyn]

I mean bunk ends . . . I guess in Canada where I live we use the word wings some times. (LOL) Anyway, I searched the site and found an old post about rust spots which recomended a product called "Whink" which is only sold in the USA, but which I was able to buy from Ebay today.
Thanks