Rust in Flue Pan

[scottw]

I have an old King 2x6 with two sets of pans (one Leader, one Grimm). The syrup pan with the newer set is in good shape. The flue pan has what I would consider to be mild surface rust, mostly on the sides of the pan. By "mild" I mean no lose or flaking rust, no pitting. The rust is fastened on but good. A brush or steel wool wouldn't do much to it without scrubbing for hours on end and even then I'm not sure I'd be able to get it all off.

I know the obvious answer is that rust is not a good thing. How much of a concern is surface rust? Should it all come off? Is any amount a bad thing? Should I not use the pans at all? Any seasoned advice is appreciated.

Thanks,
Scott

[maple maniac65]

is the rust on the sap side or on the outside?

[scottw]

There's rust on both sides, much less on the sap side. The metal is solid. Not even a hint of rusting through.

[scottw]

As I read more posts, it could be sugar sand/niter build up. These are old pans, probably tin, but not sure.

[MillbrookMaple]

It could be rust on the SS Grimm pan. I have a Grimm evaporator that is 20 years old and when I first bought it I noticed that it had some rusty looking spots. It had a couple of pin holes in my syrup pan so I took it to a local tin smith/sugar maker and he took a magnet and stuck it to the side of the pan and it stuck. He explained for a period of time Grimm used a type of SS that was Ferris because it was cheaper and easier to work with. The down side is that it will corrode. He said that I would be dealing with more and more pin holes as time went on. I had to replace the syrup pan last year and the flue pan still is leak free. I do make sure the pan stays absolutely dry in the off season and I don't use a very high concentration of pan cleaner when I clean it and I don't go crazy scrubbing the flue pan too much. I guess the moral of the story is if it is SS and a magnet sticks to it then it could be rust. If the magnet does not then it is probably nitre.