Track Power Loss

[SteveWard3928]

I am starting to build my first Garden Railway. Just for fun I decided to hook up my 4-6-0. I have noticed I am losing power on certain areas of the track (I only have about 20 feet of straight "USED LBG" connected).
The top of the rails I have cleaned. Is that where the locomotive gets its power? The inside of the rail is dirty and it looks like a dark film over the inside of the rail.  How can I get to that part of the rail to clean it.  Is there anything else that could cause a power loss. I really do not want to soder wire from rail to rail but I will if I have to.  Any input will be appreciated.  S&S

[SteveWard3928]

Corrosion  at the rail joiners. Yes there is some corrosion there. I go to take the joiner off and it does not want to come off.  Should I force it or is there a release that I am not seeing?

[SteveWard3928]

  Hunt, thanks for the tip on CLR to clean my rail joiners.  It just ate the corrosion away.  Did not even have to use my brush.