Lead Paint Durability and Rust

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Jan 19, 2021
Renton, WA
Doing a lot of research lately regarding rust repair and paint for my 1981. It seems to be a widely accepted truth that the later model FJ40's rust worse than the earlier models. All the discussions I've seen on this topic focus on the quality of the steel, making assumptions that the steel has less chromium or nickel than the earlier models. This is entirely possible. Seems weird that Toyota would have gone backwards in quality but anything is possible. This got me considering the paint. When did Japan stop using lead in paint? I believe it was outlawed in the United States for use in cars in 1978, but what about in Japan? Could this be the reason for the increased rust in the later model 40's? It seems that hexavalent chromium and zinc phosphates are still used in some paints for corrosion resistance. Maybe the true source of rust on the later model cruisers is a change in the paint formula around 1978-1979. Does lead in paint make that big of a difference in corrosion resistance? Anyone have information on this?
Toyotas rust from the inside-out, so the exterior coat of paint (leaded or not) would have little to do with how fast they rust. Under any paint job is primer, which may/may not have lead in it. So, the color coat's lead content would seem to have little to do with corrosion resistance, just from a casual viewpoint.

In a quick search, I could not find the date of any definitive ban on the use of lead in auto paints.

Toyota reduced the metal gauge on FJ40s twice during production (mid-1970s and 1979). This didn't help the rust-through phenomenon. Poor corrosion engineering (areas that trap sand/salt) is why most vehicles rust out.

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