406 Bonnet Condition
 

Hi
My 406 bonnet is showing "corrosion" or oxidation and I am looking for any member would may have a solution to "containing" the spread of the oxidation, etc? prior to painting.
There is also porosity around the corners of the bonnet. I was going to cut out and replace with new aluminium.
Any advise is appreciated.

My 406 has the same issue. I think it is a disagreement between the steel frame and the aluminium skin so the only real way of stopping it coming back is to separate the two, repair and try to prevent electrical contact when reassembling.
The other option would be to find another bonnet, but beware of anything with recent paint and consider that it may take as many hours to fit a different bonnet as it would to repair the original.

I had considered the effect of the two metals being in close proximity. I have drilled holes along the metal box section and have sprayed Schutz underseal into the section. I should know if this works after 5 years!!! Thanks for your note.