Did you read the instructions? Ferrous phosphate. https://www.rustins.ltd/images/files/1464-PDS-Rust%20Remover%20PDS.pdf
I mean...but what am i meant to do to the ferrous phosphate. Paint over it?
Admittedly thought this stuff was going to dissolve the rust away, not turn it black. Thought that was the part of "rust convertors" rather than "rust removers"
Did you read the instructions? "Before repainting clean with Methylated Spirits. Equipment should be cleaned with water".
@Belagerent started
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Did you read the instructions? Ferrous phosphate.
https://www.rustins.ltd/images/files/1464-PDS-Rust%20Remover%20PDS.pdf