Rusty breakwater in Deal, Kent

These rusty breakwaters in Deal are a big favourite with local artists, and I find their shape very appealing.
I decided to try and convey their substance in a drawing. I found quite difficult to distinguish between the rusty metal and the wooden parts of the posts. Maybe it would be better to use colour to help create a better impression of the materials.
Anyway, to make it clear what I was trying to achieve, I've added a photograph, which was taken later than the first part of the drawing, and so the light has changed.

Here's the drawing:

And here's the photograph: