This is identified by reddish-brown stains and spots on the paint surface.
- The rusting of non-galvanised iron nails, causing bleed-through to the topcoat.
- Non-galvanised iron nails that have not been countersunk and filled over.
- Galvanised nailheads beginning to rust after sanding or excessive weathering.
When painting a new exterior construction where non-galvanised nails have been used, it is advisable to first countersink the nailheads, then seal them with a top-quality, water-based all-acrylic or siliconised acrylic sealant. Each nailhead area should be spot primed, then painted with a quality water-based coating.
When repainting exteriors where nailhead rusting has already occurred, wash off the rust stains, sand the nailheads, then follow the same surface preparation procedures outlined above.