No protection with P60G2?

I must be missing something here BUT.... since the main idea behind priming the internals of our RVs is corrosion protection, why would anyone use the Sherwin Williams P60G2 primer? The P sheet states ?Does not provide significant corrosion protection.?

Look here:
http://www.sherwinwilliams.com/chemicalCoatings/dataPages/CC-A2.pdf

key word

I think the keyword there is "significant". Keep in mind that primers are usually only a surface prep so the topcoat can provide the protection. I have been using P60 with good results. Make sure you get the version with the chromate in it. Sure some of the epoxies are better but require MUCH more prepwork.