Can I appeal a fine if the signal can´t be seen well?

I have received a fine for speeding, attaching a shot of my car in the moment of the offence. It is a secondary road that I do not usually take. I was not aware that I was driving above the speed limit as I was travelling at 90kph, and when I covered the road again to check the speed limit, I saw that there was indeed a sign limiting the speed to 50kph but it was too old and the reflective material was damaged. This was the reason why I did not see it, because I was driving at night.

Can I appeal against the fine taking into account that it was impossible to see the sign?

Of course you can. They cannot fine for traffic offences consisting of not obeying signs that are damaged, or that simply cannot be seen for being located in an inadequate place or covered by obstacles. They cannot fine either when the signs can be hidden by a precedent car, if the sign is not also placed in the other side of the road.