Do I need to completely remove all rust and paint before applying the nC Corrosion Passivator Fluid?

No, sanding, blasting or sanding is not necessary. It is sufficient to remove mud and loose rust and/or paint. Since the Corrosion Passivator Fluid is applied directly over rust, it is not necessary to completely remove all rust and paint. Surfaces with well-adhering coatings remain unaffected.

More information can be found on the product page.