Ross365
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- 1,992
- Location
- UK
Accepting that all polymers will allow water molecules to get to the metal surface, what's been known for many decades is that you can mix additives in to the paint that get involved with the electrochemistry 
that goes on when oxygen and water meet iron. The electrochemistry is damn complex and I've now given myself permission to stop trying to understand it, and side-step the issue by buying paints from companies that have world-wide labs full of people who do understand it. These inhibited paints work "pretty well".
So originally there were additives like lead oxide and chromates that inhibited rusting, but they are history now, so what's the best that's on offer in 2022? I'm sure that different paint companies have their own ideas about that, but among the candidates would be zinc phosphate, and I have been using it for the past 10-12 years and have no plans to change, unless...
So when people argue strongly that the stuff to use is "epoxy primer" or Jotun 87, the question that strikes me is "never mind the chemicals that make up the binder, or the trade name, what are the chemicals that are doing the inhibiting?" I could say that the primer I use is an alkyd paint, but I think the key info that is then missing is solved by saying it's a zinc phosphate paint. So, (just out of curiosity) do the epoxies and the Jotun 87 have inhibitors in them and if so what are they?
I cleaned the dead leaves accumulated on the roof of my small steel shed (Yardmaster) yesterday. It's maybe 15 years old now and I'm quite happy with the way it's only showing only one or two small rust spots. I coated a couple of the rust spots with the old ZnP stuff a year or two back; they looked perfect
.
that goes on when oxygen and water meet iron. The electrochemistry is damn complex and I've now given myself permission to stop trying to understand it, and side-step the issue by buying paints from companies that have world-wide labs full of people who do understand it. These inhibited paints work "pretty well".So originally there were additives like lead oxide and chromates that inhibited rusting, but they are history now, so what's the best that's on offer in 2022? I'm sure that different paint companies have their own ideas about that, but among the candidates would be zinc phosphate, and I have been using it for the past 10-12 years and have no plans to change, unless...
So when people argue strongly that the stuff to use is "epoxy primer" or Jotun 87, the question that strikes me is "never mind the chemicals that make up the binder, or the trade name, what are the chemicals that are doing the inhibiting?" I could say that the primer I use is an alkyd paint, but I think the key info that is then missing is solved by saying it's a zinc phosphate paint. So, (just out of curiosity) do the epoxies and the Jotun 87 have inhibitors in them and if so what are they?
I cleaned the dead leaves accumulated on the roof of my small steel shed (Yardmaster) yesterday. It's maybe 15 years old now and I'm quite happy with the way it's only showing only one or two small rust spots. I coated a couple of the rust spots with the old ZnP stuff a year or two back; they looked perfect
.
