It's a nice find. I like the streaks of color. I like the rusted lock and hinge. It's intriguing and I can see why you photographed it.
I'm thinking a 6 for the following reasons: intriguing, lovely colors, interesting movement. Why it's not higher: I'm not finding anything deeper to it. It draws you in nicely, but it doesn't keep you. Once you've explored it, I think you'd end up being done. To me art is a continual discover or joy. Something that draws you back. Something that gives you joy, anguish, excitement, etc. each time you see it.
I am unsure whether this photo is a bit out of focus or whether my eyes are getting tired, but I think it is the former. I like the colors, patterns on the hinge and boards, and the rustic feel of the image.
Close to abstract art, with subtle and soft colors harmonizing nicely. Interesting how the glob of paint above the keyhole resembles an eyelid. I can imagine seeing this framed and displayed in an office reception area.