The Skipper's Blog

Ask The Skipper
Views Counter

How Do I Fix Alumetron Below The Waterline?


Jack B ​asked:

With Alumetron I am a Happy & Unhappy customer.

To this email I have attached 5 pictures.

In Feb 2018 I bought a new Tahoe Pontoon Boat. Two pontoons.

In Spring 2019 I was very unhappy with the boat as the pontoons had tarnished terribly. They were brown.

Using an Aluminum Brightener chemical product, I acid washed cleaned the pontoons. They looked brand new.

Aluminum Brightener, Product # G-200, Industrial Strength Mag & Drive Cleaner
Tri City Chemical Co., Spindale NC. Ph 828-245-5896.
** Label Reads: Contains Hydroflouric Acid

Then over a weekend (2 coats on Saturday 2-3 hrs apart and 1 coat on Sunday) I applied 3 coats of Alumetron.

Then the boat sat on the trailer for 4 days before I launched the boat into the lake.

I live on Lake Murray in Lexington SC USA. Between Late April through end of October the boat is in the water at the dock.

Happy: Above the water line my pontoons look great. Very Pleased.

Unhappy: Below the water line within a week the pontoons had a whitish look to them.
When I take the boat out of the water, for days/weeks/months, they continue to have a white look below water line.

Two years later, soon I will want to put the boat in the lake for the season.

QUESTION 1: Did I allow enough time between coats? I do not recall it being a wet rainy or humid weekend.

QUESTION 2: Why did the Alumetron turn white under the water line?

QUESTION 3: Is Alumetron suitable for submersion in the lake water for 3-4-5-6 months?

Now I am trying to determine what to do.

Left unprotected the aluminum will tarnish again.

I like the look of the Alumetron coated pontoon above the water line.

I look forward to your reply. THANK YOU.


For your convenience, I’ve highlighted the hyperlinks. Click on the hyperlink to get more information about the selected product.

Hi Jack,

Solving your problems may be a little tricky because you are mixing and matching products from different manufacturers and there could be some compatibility issues. All Aurora products are System Matched to work well, one with the other. This is not always the case when you try to use products from different manufacturers and this can sometimes have undesirable consequences.

Alumetron is designed to bond chemically to aluminum and in order to do that the aluminum must be clean and dry and free of any pollutants. When properly applied, overcoated with VS721 and maintained, Alumetron can protect your pontoons against corrosion and keep them looking shiny and new for up to 10 years. Alumetron and VS721 are both proven to work in constant water immersion as well as above the surface.

The instructions on the bottle of Alumetron tell you to apply 4 coats. Apply subsequent coats only when the previous is dry. It’s the ideal quantity, not 3 and not 5. Under ideal temperature and humidity conditions, you need to allow the Alumetron to cure a minimum of 96 hours before applying VS721. Longer if the temperature is cooler or the humidity is higher than specified in the instructions on the bottle. After the cure period, you can apply the VS721, again following the instructions on the bottle.

I know that it sounds involved and a bit complicated but it’s really not. Just requires a bit of patience and considering that this protective coating can last up to 10 years, it’s definitely worth the effort. There is no other coating that will give you this kind of protection and none that gives you a warranty against cracking, peeling or yellowing for up to 5 years, when properly applied. Mixing and matching products, voids the warranty.

PIC 5 Shows the back right corner of boat.

The whitish color that you are getting below the waterline is called blushing. This indicates an application problem. The Alumetron has not properly bonded to the aluminum and water has entered the interface between the substrate and the coating or that the Alumetron was not allowed to cure properly before application of VS721, or before water immersion, and water (which is the green solvent in Alumetron) was not allowed to completely evaporate and remained in the coating. Improper bonding can be caused by pollutants on the surface of the aluminum when you applied the Alumetron or improper curing before applying VS721 or launching the boat.

Stripping the Alumetron with lacquer thinners will leave a residue which needs to be removed as new Alumetron will not adhere properly to the lacquer thinner residue. To remove the residue, first wash the surface thoroughly with a 50/50 solution of Boat Clean Plus and Isopropyl Alcohol and rinse well. Next wet the surface with fresh water and spray on Boat Clean Plus and wash again and rinse clean. When rinsing note that the water sheets and does not bead. If you see beading that indicates that some pollutants are still present and the surface needs to be washed again.

The issue now, is how to correct the issues that you have. The aluminum cleaner that you used is industrial strength and industrial cleaners will etch the aluminum and leave a whitish or faux anodized look instead of the bright aluminum look of new mill finished aluminum.

Normally, if you had used only the Aurora System Matched products, I would recommend that you buff out the area below the waterline, and areas where you have damage from rubbing against dirty fenders, with Alumabuff and then touching up those areas with Alumetron and VS721 only, but now, the problem would be a very obvious difference in coloration. The buffed area would look silver while the etched areas, undamaged above the waterline would still look whitish.

To illustrate, I’m attaching before and after pictures of another customer’s boat. In this case, his dealer sold him the wrong product to remove the algae (an industrial strength aluminum cleaner) and it etched the aluminum. The restored silver look is after he buffed with Alumabuff and applied Alumetron and VS721.

Customer's Restored Pontoon Before and After

So, you have two options:

1. Strip the entire pontoon, buff it out with Alumabuff and then re-apply Alumetron and VS721 to restore the original silvery finish.

2. Try some experimenting, but do tests first on the inside of the pontoons to make sure you’re getting the results that you want before doing the entire pontoon. There are no guarantees as you’ll be mixing and matching products again, but it may be worth the try if you like the appearance that you have above the waterline.

a. Reapply your industrial aluminum cleaner below the waterline to see if it will remove the stains and match the appearance above, then clean the surface very well with Boat Clean Plus and alcohol as above. In the damaged areas, you can try to buff out those areas with Alumabuff and a Marine Power Mitt and then try to etch those areas with your industrial cleaner to try to match the surrounding area and then clean as above and reapply the Alumetron and VS721 to those areas. The damaged areas seem to have some scuffing or abrasion damage and it’s unlikely that your industrial cleaner will remedy those without some buffing to even out the areas.

b. If your industrial cleaner will not remove all the stains below the waterline, you can try to buff the area below the waterline with Alumabuff and then try to re-etch that area to see if it will match the color, but test first.

c. Strip the entire pontoon, re-etch it with your industrial cleaner, clean it well, as above, to remove all pollutants, and then reapply the Alumetron and VS721.

PIC 4 Shows the dirty pontoon under the boat. How do I clean this Alumetron coated surface?

As far as the algae on the inside of the pontoons, use Algex to remove that. It will not attack Alumetron and when used properly will remove the algae without affecting the finish of the aluminum. You can watch the How To video on our Website.

Thanks for your question,
Captain Aurora
Richard Kittar

The Skipper Recommends The Following System Matched Products:
More Info
More Info
More Info
More Info
More Info