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topic 49880

Aluminum horse trailer corrosion protection

A discussion started in 2008 & continuing through 2017 . . .

September 1, 2008

Q. Have a aluminum horse trailer with floor stains that horse urine has discolored & believe has eaten a small hole thru metal, also the painted exterior has peeled in several spots. Would like to repaint in needed areas & protect floor for the future. HELP. Thanks.

John Lee
buyer - Pasadena, Texas

3M Marine Sealant

May 19, 2014

Q. Thank you in advance for your advice. I want to protect the floor of my all aluminum horse trailer. The floor is subject to urine, and friction from shod horses. The usual method is to cover the floor bids three-quarter inch rubber mats. That the urine runs down and pools underneath the mat causing corrosion. My horse urinates every single time he steps into the trailer. The mats are heavy and awkward to clean and get dry on both sides and rinsing the trailer after each use. Is there a sealant that will flex under the weight of the horses without cracking? I am considering removing the mats and replacing them with chipped rubber pebbles. This can be shoveled out and rinsed when soiled. But I still need to protect the aluminum underneath. My other option would be to spray in a hard surface such as a rhino liner. Do you have any suggestions?

Jean Lukens
Equine - Leverett, Massachusetts USA

May 2014

A. Hello Jean. From the way you have described it, this sounds to me like an ideal application for a rhino liner type coating.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

June 24, 2016

A. Black Rubber barn matting is what is causing the corrosion on the aluminum trailer floors. I have seen this many times.
What is happening is Galvanic corrosion cause by dissimilar metals
Graphite (LEAD) is added to the rubber to make it black. Black rubber will eat up aluminum in short order unless it is isolated. With multiple coats of epoxy primer.

I have seen this happen many times on commercial aluminum boats with black D-rubber bolted to exterior of the vessels.
The aluminum behind the Black D-Rubber will eat out in not time. We use GREY D-Rubber and there is no graphite to eat the aluminum.

Steve Daigle
Daigle Welding & Marine LTD - Campbell River, BC, Canada

February 18, 2017

Q. Hi Steve, I don't know if the dissimilar metals is a factor on our horse trailer. We have an aluminum deck that has been coated with a rubberized bedliner like Rhino. On top of that was laid the thick black rubber mats. The trailer is about 14 years old and after acquiring, I removed the thick rubber mats to find the Rhino lining had separated from the aluminum. I peeled it up to find corrosion on the aluminum in some areas and spotless aluminum in others.

Since the black rubber mats were not in contact with the aluminum and galvanic reaction requires an electrical path which was not provided due to the Rhino, I suspect that the oxidation is a result of two things; urine leaking through and propagating along the interface between the Rhino and the aluminum and from water leaking up from the bottom through the joints and rivets.

I believe the Rhino linings may be helpful but I am inclined to remove the oxidation then apply some other type of coating such as epoxy. Since the rubber mats will protect the coating from abrasion and the epoxy is providing electronic isolation (relatively speaking), I think that things will be better.


Ken Shannon PE
erex engineering - Camden Point

April 25, 2017

A. Hello Ken

Very interesting question regarding Rhino Bed liner as a insulator between the rubber and the aluminum floor and why you still have corrosion.
I have been spraying Polyurethane insulation/floatation in my Eaglecraft aluminum boats for 32 years. About 25 years ago I discovered that the polyurethane was having a chemical reaction under the waterline where it is exposed to moisture with the aluminum; 1/4" aluminum bottom plate was being being eaten away and in some spots right through.
At the time I knew a corrosion expert with the Canadian Navy.
We discussed this in great length and after research it was concluded that if I were to continue to apply polyurethane in the boats I would need to insulate the bare aluminum from the hull.
We have since been using a thick BARRIER coat of Epoxy paint to the aluminum prior to spraying the Polyurethane.
Since we started doing this we have not had any more problems with corrosion.
I googled Rhino Liner and found that it is a Polyurethane product.

Steve Daigle
Daigle Welding & Marine, EagleCraft Boats - Campbell River BC Canada

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