GG’s,

Has anyone tried Flood Penetrol on a japanned tool?

This is not a rhetorical question.  I use Penetrol only as a paint additive to
improve brushability.

I note that the label refers to other uses and a quick Bing search turned up
various testimonials on using it as a rust-preventive coating and also as away
to _restore faded black plastic exterior trim on automobiles_.

Note the similarity between the description of the discolored spot on the OP’s
#20 and the appearance of sun-faded black plastic.

If Penetrol doesn’t harm japanning, it can likely improve the appearance and
provide rust-resistance to boot!

John Ruth
Who just added automotive “Swirl Mark Remover” to his shopping list, per Scott.