I am often being PM'd and asked about aluminum floor corrosion, how it should be treated and if its maintenance can be reduced. The first issue is some terms that I believe are confusing. Aluminum oxidation and corrosion.

Oxidation is the microscopically thin, naturally occurring surface coating that appears whenever bare aluminum is exposed to the air. This coating is what makes aluminum so resistant to environmental damages. Its oxide has a dull grayish silver colour, and it's this coating that acid washes and "brighteners" remove, to restore the new bare aluminum look. Unfortunately this process again starts as soon as the metal is once again exposed to the air. Only by a coating of waxes or surfactants, can air be kept from the surface, and preventing a reoccurrence of this dulling. The acids commonly used in the washing process, are mild, and clean the metal surfaces. They are usually not strong enough to treat and stop active corrosion.

Corrosion is seen in pitting, some black, some white and often an accumulation of fine powder around the affected area. This is as destructive to aluminum as rust is to ferrous materials. Often too, when a small area is detected, a larger problem is hidden. This has to be chemically or mechanically cleaned and repaired before any covering is placed over it. To not do so would be akin to painting over rotted wood.

The product I chose to coat my trailers' flooring is Duplicolor truck bed liner, commonly sold by auto parts stores and Walmart. If you check the home pages of Herculiner and Duplicolor, you will find both products are very similar in their chemical make up. Since I have not used Herculiner, I can only state that several people have done so, and are pleased with the results. I chose Duplicolor because of is availably at our local Walmart for less than half the advertised, mail order only availability of the Herculiner. My local sales tax is far less than the shipping charges.

To install these products,you have to first chemically stop the corrosion before you can apply any coating over the bare aluminum. This is done by acid etching. I use Muriatic acid that I purchase from Lowes. Sweep the floor and pressure wash if possible, you do not have to scrub any contaminates. Move the trailer to an outside area. Do not apply this acid inside any closed structure, barn or garage. Open all the trailer windows, close the pass thru door to your LQ. One or several box fans aimed appropriately are also good option.

Muriatic acid is mild and effectively stops active corrosion. If the corroded areas penetrate the thickness of the metal, they have to be mechanically cleaned out with drills or a rat tail file until the area shows only bright metal. Two part epoxies can be used as fillers (JB Weld or equivalent) and can fill smaller holes; larger repairs should be made using an aluminum welding apparatus. If the smaller holes are first reamed with a countersink, it will give more strength to the repair.

YOU MUST USE A CHEMICAL RESPIRATOR TO APPLY THIS ACID. It costs about $40 and incorporates a charcoal filter. A dust mask is worthless with the resulting fumes. Wear old shoes, long pants, gloves and safety glasses.

Pour a liberal coating of some acid on about a third or quarter of the floor area, and quickly spread  it around with a short bristle brush and long handle. I use a roof coating brush. You will immediately see fumes rise from the floor; leave the trailer quickly. The acid will start showing bubbles after a minute or two. After about 10 - 15 minutes you will see an even foam of bubbles, with the most reaction being where the floor was the most corroded and dirty. Re-enter the trailer and agitate the wetted area with the broom and leave it for another 5 minutes. Rinse the floor with water and inspect the area, spot reapplying as necessary until the floor is an even color, and there is no black or brown spots in the corroded areas. The cracks and seams between the floor planks, should be especially treated with a fair amount of acid. Unseen corrosion can be trapped in these areas, and will ruin a new coating if not adequately treated.

Do another third and the last the same way, working towards the door as you go. When you're done flood the floor several times with water. Let it dry overnight and the next day you can apply your coating. On aluminum, by acid washing the area, you are providing a clean, ready surface to be coated. It is now etched and corrosion free. On steel, the Duplicolor manufacturer recommends that all the areas are sanded, abraded and cleaned before any application. Read all of the manufacturer's instructions for the proper procedures.

The Duplicolor manufacturer recommends two coats of coverage. On a three horse trailer with a rear tack, one gallon will give you a two coat coverage. I bought two gallons and put down three coats, and kept the rest for other projects. The large brush is used to apply the product around the edges of the floor. A paint roller, now equipped with the same handle used with your roofing brush, will make short work of applying the subsequent coats of new bed liner material.

Several seasons ago I treated the aluminum stall floor of our new to us, Sidekick trailer with this product. Two years ago I similarly coated the aluminum flooring of an Exiss used trailer we had just purchased. Neither trailer had been acid washed by their previous owners. Since then, at the end of each season, the only maintenance to the floors has been to roll the mats over and hose the floor down. The coating continues to look new, and with the mats on top, has no chaffing issues. I also coated the steel dump bed of our utility vehicle. This liner is constantly being subjected to all sorts of abrasion, urine, manure, stones, dirt and after three years, shows no wear or chipping.

Two gallons of "Duplicolor", one gallon of acid, a roller cover, and one cheap paint brush, costs about ~$100. Actual work time is two or three hours, the rest is waiting for things to dry. A four horse trailer floor could be easily coated with two gallons (three coats).

Best of luck   Gard

After the floor is treated with the acid, it is etched and clean. Both are necessary for a proper bond of the bed liner material to the aluminum. After the floor is cleaned, and the metal is not coated, it will  begin to oxidize. When this happens, the surface will have to be once again acid treated before any coating can be applied.

If you don't have two days now, I would recommend waiting until next year and do the whole project at once.

Gard

A while ago I updated this thread with a new posting. There are a few changes that I thought would be pertinent.

Gard

http://www.horsetrailerworld.com/forum/thread-view.asp?threadid=12471&posts=12