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Aluminum corrosion and white powder on a horse trailer

White powder, pitting or pinholes on an aluminum horse trailer floor are aluminum corrosion, driven by urine and manure trapped under the mats. Caught early, it is a wash-and-treat job. Past that, aluminum floor work runs about $12 to $20 per square foot around Ocala, and local damage can often be patched instead of replacing the whole floor.

Check this first

  1. Pull every mat. Corrosion lives under them.
  2. Wipe the white powder with a rag and look underneath. Light surface oxide with solid metal underneath is early. Pits you can catch a fingernail in are deeper.
  3. Probe the worst spots gently with a screwdriver. Any give, any hole, any crack is past cleaning.
  4. Look from below with a flashlight at the crossmembers and the welds where the floor meets them.
  5. Check where water sits. A trailer parked nose-down holds water at the front; one with a blocked drain holds it in the low spots.

What is usually wrong

What you findLikely causeFix and typical cost
Light white film, solid metalEarly corrosionWash, dry, treat; follow the maker’s schedule
Pitting in a few spotsUrine pooling therePatch and coat, quoted after inspection
Holes or soft areasCorroded throughSection or full floor, $12-$20 per sq ft
Crossmember corrosionFrame under the floorCrossmember repair, quoted separately
Water standing after a washPoor drainage or nose-down parkingRaise the front to drain, per Exiss

Full ranges are on the pricing page and the floor calculator.

What the makers say

Every aluminum horse trailer maker we cover has a floor schedule, and the differences are worth knowing:

  • Sundowner: remove the mats every sixty days and wash thoroughly “to prevent severe floor corrosion”. Remove mats before acid-washing and rinse thoroughly before they go back, or the warranty is void.
  • Featherlite: remove the mats and wash them at least every three months.
  • Exiss: power wash the floor at least every three months with the front raised for drainage; let it dry before the mats go back; treat with an anti-acidic such as baking soda.
  • 4-Star: every 6 months or 6,000 miles, mats out, floor cleaned and rinsed, mats back once dry.

One flooring guide recommends that on an aluminum floor the mats come out and the mats and trailer be rinsed and fully dried at least five times a year.

Why it matters

Aluminum floors are light, but corrosion thins them from the top down where you cannot see it with the mats in. A floor that looks fine from the ramp can be weak where the horses stand.

When to call

Any pitting deep enough to catch a fingernail, any give under a screwdriver, any corrosion on the crossmembers. See trailer floor replacement, horse trailer repair, and the brand pages for Featherlite, Sundowner, Exiss and 4-Star.

Frequently Asked Questions

What is the white powder on my aluminum trailer floor?

It is aluminum corrosion. On a horse trailer floor it forms where urine and manure sit, especially under rubber mats that stay down. Flooring guides note horse urine is acidic and corrodes aluminum floorboards over time.

How do I stop it?

Follow your maker's mats-out schedule: Sundowner every sixty days, Featherlite and Exiss at least every three months, 4-Star every six months. Wash the floor, let it dry fully before the mats go back, and Exiss suggests treating the dry floor with baking soda to reduce the effect of urine.

Can a corroded aluminum floor be patched?

Often, if the damage is local. Posters on a horse trailer forum suggest patching or plating over just the damaged horse area instead of replacing the whole floor. Full aluminum floor work runs about $12 to $20 per square foot.

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