That is a toughie. I have tried before with very little success. Soak the coin in some motor oil or penetrating oil. Brush with a toothbrush. The toothbrush has a chance to scratch it by scooting the rust particles around, so you might just want to rinse it with something like xylene.
Coming from my automotive background, there are plenty of ways to arrest what's going on. All of them will damage the original surface of the coin. But the rust has already damaged the surface. Oil based products would be my first suggestion but anything you use is going to do some damage.
Upon closer inspection, your coin is not a 1945. The 5 in the date is altered, and poorly at that. Completely wrong shape/font/size. It looks more like someone possibly altered a 1943, or just removed the last digit and replaced it altogether. The rust could have been purposely added to try and hide evidence of tampering, as is often the case.
Just bought it off E-Bay , user name peter34v5 , good eye , haven't got the coin yet .yes i seen some copy ones before .thanks guys stay alert !!