One vs Two component Zink chromate/self etching primer?

[andreas.mehlin]

Anyone here who knows how big difference there is between a single component and a two component zink chromate or self etching primer?

...it's for aluminium and will be coated with epoxy primer and two pack polyuruthane

[MikeFergie]

I think the two pack will have a hardner allowing for it to dry better

[roverhi]

Used one part zinc chromate primer on two part polyurethane painted aluminum bits. Worked fine on backing plates below decks. Above deck, paint has begun to bubble significantly after 8 years. Sanded/brushed the parts to bright metal but didn't use an etching solution before painting. Non visible below deck backing plates were just painted with one part Zinc Chromate primer and also look fine.