Rust around the bathtub drain is almost always on a porcelain-over-steel or porcelain-over-cast-iron tub. The porcelain coating has chipped or worn through at the drain area — either from the drain hardware, cleaning abrasion, or impact — and the metal underneath is exposed to water.
Left alone, it keeps getting worse. Treated now, it’s a $20 fix. If the rust-through is more extensive than surface damage around the drain, see repair options for a rusted-out bathtub for a full assessment of your choices.
Assess the Situation First
There are two different problems that look similar:
1. Surface rust around the drain flange — The rust is on the tub surface, near the drain. The drain hardware itself may have left a rust ring, or the porcelain has chipped at the drain edge. This is the common, easy-to-fix case.
2. Rust through the drain area floor — The tub floor has rusted through entirely, meaning there’s a hole or near-hole in the metal. This is a different problem — see below.
Press gently on the rusty area. Does it flex or feel soft? If yes, the metal underneath may be compromised. If it feels solid, you’re dealing with surface rust and this guide handles it.
What You’ll Need
- Rust converter — Rust-Oleum Rust Reformer or similar
- Rust-inhibiting primer (if you’re going to top-coat)
- Bathtub chip repair kit — for filling and color-matching after rust treatment
- 400-grit wet/dry sandpaper
- Wire brush or Dremel with wire wheel — for removing loose rust
- Isopropyl alcohol
- Nitrile gloves
Step 1: Remove the Drain Hardware
Take out the drain stopper and, if possible, the drain flange. This gives you clean access to the full rust area and prevents you from coating over the drain threads.
Most drain stoppers pull straight out or twist out counterclockwise. Drain flanges require a drain key tool — see how to remove a drain here.
If the drain hardware itself is rusty, this is a good time to replace it. A replacement drain assembly runs $10–20.
Step 2: Remove Loose Rust
Use a wire brush or wire wheel attachment on a Dremel to remove all loose, flaking rust. You want to get down to solid metal — not polish it, just get rid of anything that would come off on its own.
Wipe clean. Vacuum up the rust dust.
Step 3: Apply Rust Converter
Rust converter (like Rust-Oleum Rust Reformer) chemically converts active rust to a stable compound. It doesn’t remove rust — it stabilizes it so it can’t keep oxidizing.
Apply with a small brush, following the label instructions. It typically turns black as it reacts. Let cure fully — usually 24 hours.
Important: Don’t skip this step and go straight to a coating. Coating over active rust just traps the oxidation and it continues underneath — you’ll be back to square one. This principle applies to the full refinishing process too — the DIY bathtub refinishing guide explains why prep work is the single most important factor in a lasting finish.
Step 4: Fill and Level
Once the rust is converted and fully cured, the area will be rough and slightly recessed where metal was lost. Fill with a bathtub chip repair compound or a 2-part epoxy filler.
Apply in thin layers, building up to surface level. Sand level with 400-grit once cured.
Step 5: Color Match and Finish
This is the cosmetically tricky part. The repaired area needs to match the surrounding tub.
For white porcelain, a Rust-Oleum Tub & Tile touch-up applied carefully and sanded smooth will blend acceptably on a clean white tub. On a tub that’s yellowed or discolored, the white patch will stand out.
The best solution for a tub with widespread rust plus general aging? Repair the rust, then refinish the whole tub. The full refinish gives you a uniform surface and the rust is properly sealed beneath it.
When Is It Too Far Gone?
If the drain area has rusted through completely — meaning there’s an actual hole or the metal is paper-thin and crumbling — you’re past what a repair kit can address. Options at that point:
- Replace the tub — The most thorough solution. A rusted-through tub floor has structural concerns.
- Professional restoration — Some restoration companies can weld and repair tub floors, though it’s rarely cost-effective vs. replacement.
- Fiberglass patch — For a temporary hold, a fiberglass repair kit can patch a through-rust hole. This is a band-aid, not a fix.
Preventing Future Rust
Once repaired and refinished, keep the drain area dry between uses when possible. Replace a worn drain stopper that holds water against the tub floor. Avoid abrasive scrubbers on the porcelain surface, especially around the drain.
How to take care of a refinished bathtub →