Corrosion of steel downpipes

Cause

Moisture cannot readily drain away from around a bracket

Repair

  • remove loose rust by sanding or wire brushing; apply either an acrylic corrosion-inhibiting primer where the metal is not exposed to a high corrosion atmosphere, or a zinc-rich primer in high corrosion zones; paint with a minimum two coats of acrylic latex paint
  • if there are large holes the downpipe it should be replaced; small holes may be covered with duct tape as a temporary repair
  • replace incompatible metal with a suitable metal or PVC downpipe

Cause

Moisture cannot readily drain away from the downpipe seam

Repair

  • remove loose rust by sanding or wire brushing; apply either an acrylic corrosion-inhibiting primer where the metal is not exposed to a high corrosion atmosphere, or a zinc-rich primer in high corrosion zones; paint with a minimum two coats of acrylic latex paint
  • if there are large holes the downpipe it should be replaced; small holes may be covered with duct tape as a temporary repair
  • replace incompatible metal with a suitable metal or PVC downpipe

Cause

Incompatible metals such as copper guttering with a galvanised steel downpipe

Repair

  • replace incompatible metal with a suitable metal or PVC downpipe

Cause

Material at end of its serviceable life

Repair

  • replace downpipe

Cause

Wrong specification for the environment

Repair

  • remove loose surface rust by sanding or wire brushing; apply either an acrylic corrosion-inhibiting primer where the metal is not exposed to a high corrosion atmosphere, or a zinc-rich primer in high corrosion zones; paint with a minimum two coats of acrylic latex paint
  • if there are holes the downpipe should be replaced; small holes may be covered with duct tape as a temporary repair
  • replace incompatible metal with a suitable metal or PVC downpipe