How to clean this, any ideas?

[Sdfish]

Any ideas on how to clean this up a bit?

 

[PointedRose]

Mix vinegar and water in a spray bottle

 

[seasick]

I think it may be too far gone to clean up. It looks pitted . Try the vinegar as suggested and see what happens but I don't expect a big improvement.
I have had some luck with similar cases by sanding off the corrosion right down to the base metal and then priming and painting the arm, You can get 'chrome' looking paint but any color will do.
If there are holes with the pitting, they can be filled in with MarineTex or even Bondo and sanded smooth, then painted.

 

[Sdfish]

Thanks for the tips guys!

 

[Fishtales]

Don’t think most will clean off. Maybe you can get a new one. Check with Sim Yamaha.

 

[PointedRose]

I’d definitely try what seasick suggested. Go with very high grit sandpaper