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3,961 Posts
Discussion Starter · #1 ·
I decided to go and post it anyway, as I'd most likely forget, due to your requests.

1 Coat all interior surfaces with 5 or 6 coats of rolled epoxy

The inside of the tank should be treated similar to the outside of a
hull. We recommend a minimum of 20-mil coverage, which is five or six
rolled coats of epoxy, for all interior surfaces of tanks. This is
similar to the coverage recommended as a "barrier coat" for the
exterior of a hull. After it is rolled on, brush the epoxy out to
minimize any entrapped air. Install surge baffles to minimize free
surface effect, using generous fillets and giving them the same 5-6
coats of epoxy as the rest of the tank interior.

Any tank openings, such as fill, vent, inspection or clean out, should
be oversized and also receive 5-6 coats of epoxy. We recommend that
fasteners be epoxy bonded in place to secure any hardware to the tank or
in the construction of the tank (See details of hardware bonding in the
WEST SYSTEM User Manual & Product Guide.)

2 Use a slightly resin-rich/ hardener-lean epoxy mixture

Carefully metered resin/hardener ratio is critical to any epoxy's
performance. In all projects, with one exception, we recommend
dispensing and mixing epoxy at the target ratio within our acceptable
range. Tank building is the exception to the rule. When mixing epoxy for
tank coatings, we recommend a resin-rich/ hardener-lean mixture at the
outer limits of the acceptable range as shown in Table 1.

This is because excess resin in epoxy is less likely to adversely
affect the physical properties of cured epoxy than excess hardener. When
excess hardener is in the epoxy matrix, it cannot fully react with the
resin and will become suspended in the mixture. Because amines (in the
hardeners) are water soluble, they can potentially leach out and cause
odd tastes, contaminates in the liquid, and porosity in the epoxy film,
among other performance defects.
The maximum resin-rich ratios noted in
Table 1 are at the end of acceptable ranges for WEST SYSTEM epoxy. These
ratios should not be taken any farther from the target. These maximum
resin-rich ratios meet specification to obtain a properly cured epoxy
film and to minimize extracts leaching out of the epoxy. When using 300
Mini Pumps, one way to obtain the resin-rich/hardener-lean ratio within
the acceptable range is to dispense the following:

Epoxy Combination Pumps Resin Pumps Hardener
105 Resin +205 or 206 Hardener 6 5
105 Resin +207 or 209 Hardener 7 6

3 Mix thoroughly, using a double-pot method

We recommend using a double-pot mixing method when building or coating
tanks. Completely thorough mixing of epoxy is difficult to achieve when
resin and hardener are pumped and mixed in one container. A film of
resin or hardener will cling to the bottom or side of the container
leaving areas of unmixed or undermixed components. This can be readily
seen when tinted epoxy is mixed together.

To ensure thorough mixing, first dispense and mix resin and hardener in
one container, carefully scraping the sides and bottom. Scraping is key
because it incorporates the majority of the single components into the
mixture. Second, transfer this mixed epoxy into another clean mixing
container. Use a new stir stick to mix a second time. This transfer will
eliminate any clinging unmixed material and additional mixing will
assure thorough crosslinking of both components.

4 Post cure at an elevated temperature

Post cure at a minimum of 120 F for 4 to 8 hours (after the epoxy has
cured at room temperature and can no longer be dented with your
You can use a temporary oven or radiant heater to apply an
elevated temperature post-cure. A high-wattage incandescent or halogen
light bulb can raise the temperature in a tank high enough to do the
job. This is often the only way to do an integral tank. However, watch
the fire hazard as some light bulbs can get hot enough to cause the
epoxy to char or possibly ignite. Alternatively, allow the coating to
cure for 2 weeks at room temperature.

5 Scrub cured epoxy thoroughly with water

Scrubbing with water and a scouring/abrasive pad, such as 3M's Scotch
Brite* pad, removes any surface contamination, specifically any
potential amine blush that may form on the surface. Amine blush is
water-soluble and can be removed with tap water. The scrubbing action
agitates the surface to help removal.
Solvents don't normally remove
the amine blush because of its water solubility. So leave the lacquer
thinner, acetone, vinegar, alcohol, and other solvents in the storage
bin, and use water. After scrubbing, rinse again with water and dry with
paper towels.

If you have any questions, please feel free to call.


Bruce Niederer
Tech Advisor

Gougeon Brothers, Inc.
100 Patterson Ave., PO Box 908
Bay City, MI 48707-0908 U.S.A.
fax: 989-684-1287
West System toll free phone:
Proset toll free phone:
URL: or

wow thanks...

the timing couldn't have been more perfect for me... i'd just ordered the west systems epoxy a few days ago, and was really getting concernde about this exact issue.

again.. thanks


· Registered
3,961 Posts
Discussion Starter · #5 ·
I've posted in the Feedback forum to request that it is made sticky.

It better be, because I will additionally be posting pics of a step by step process how to make epoxy coated tanks made of wood. Also, how to make styrofoam/great stuff coated with epoxy.

I will be working on my tanks in the garage first thing in the morning.

Spring Break is here!

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3,961 Posts
Discussion Starter · #6 ·

According to West System:

Epoxy can be applied over latex paint. HOWEVER, if the surface that the latex paint is sticking to is undermined, epoxy's strength will be compromised. Meaning, the latex paint becomes the weak link.

Epoxy will stand up underwater for very long periods of time when it is not subject to UV radiation.

The representative told me that they have some users that have some boats that haven't been coated for 30+ years, and that is in saltwater (which is corrosive).

Others, who have boats in more shallow water, report having to have to coat more frequently.

A word about fillers to thicken epoxy. Microfillers (I think its product 403), are made of cotton. Epoxy's strength is around 11,000 psi, but adding this product will reduce it to about 7,000 psi. While still pretty strong, depending on fillers, the strength will decrease. The high density colloidial silica is the most powerful and can potentially strengthen epoxy (according to the representative)

I asked about the fillers because some of you folks may want to thicken epoxy into a paste to smear on. It would definitely give a more textured look and enhance your rock formations.

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610 Posts
a quick note:

First, thanks to west marine for responding to, and answering such a request, that's nice to see. Second, thanks to Rain_Frog for sharing.

On the curing time/temp: an easy way to achieve the 120 temp for me was to leave the epoxied pieces in my car at work today. The inside temp reached just under 140, and maintained 120+ for at least 6 hours. That was a much easier solution for me than trying to achieve that any other way. Hope that helps future explorers...

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3,961 Posts
Discussion Starter · #8 ·
an even easier way is to do it on a hot summer day. Since you will throw soil/sand/ etc. which is dark, it will definitely get REAL would be amazed how fast it cures from solar absorption! I've had it smoke once when a tiny blade of grass accidently fell onto it from the wind!

When its done, and you've added enough sand/clay soil coats, (and sand it to make it smooth) its hard to tell which is the real thing, and which isn't...once again, I never got to complete the tank...just the background and DIY chiller! :roll:
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