That looks like cast iron appearance you can apply it by assigning cast iron material to the part, by default the appearance is black but you can change it by going to appearance tab and editing the appearance.
1. Apply material i.e cast iron
2. Go to appearance tab.
3. Right click appearance and edit appearance
4. Play with colors.
If you do not want to assign material then you can just download the cast iron texture from Google and follow the steps below.
1. Download the texture.
2. Go to appearance tab and right click in the blank area then add appearance
3. Select the advanced tab there is option to browse, select the texture you just downloaded
4. Select the part/face or feature you want to apply on.
5. Go to mapping and play with the width and height.