Atlanta Painting

This article is relevant to me right now because we are using Sherwin-Williams’ Macropoxy 646 on a metal fountain in a condo community.  I still need to apply another coat of the Macropoxy before we finish, however, I can’t get decent weather long enough to apply the final coat.  After one coat, the fountain looks awesome.

This condition of this fountain was quite bad.  It was approximately 80% covered with surface rust and badly pitted.  It had not been cleaned since 2001 and the inner bowls were covered in algae.  It took be about a dozen phone calls and two days to figure out if we even wanted to take this job.  Once I decided that I was going to do the job, figuring out what to put on it was another challenge.

Our Atlanta painters are good, but in a situation like this, you need to do extensive surface preparation and you MUST use the right coatings.  We are dealing with previously coated ferrous metal, covered in rust, that will be used for immersion service.  Alone, each one of these variables requires attention, but together they create a “perfect storm” of potential coating failures.

Here is a rundown of the variables that must be addressed:

1. Ferrous metal - They are always prone to rust.
2. Previously coated with unknown coating - Can create compatibility and adhesion problems, limiting the coatings that can be used.
3. Badly rusted - You cannot paint or prime on top of unprepared rust because if the rust isn’t stopped, it will grow underneath the topcoat causing it to lift and fail.
4. Immersion service - Very few coatings can be used underwater.  Combining this with the fact that the substrate is metal and already rusting further limits the coating which can be used.

The 100% correct way to handle this is to disassemble the fountain, have it sand blasted to sspc-sp10 white metal blasting preparation, and then recoat it.  This process is more expensive than replacing the fountain.  I explained this to my customer and came up a much more cost effective solution.

Here is what I did:

1. I got a 3500 psi pressure washer with a rotating tip and pressure washed the entire fountain.  This removed the algae, loose rust, and loose paint.  I let the fountain dry completely.
2. I then applied a coat of Ospho.  Ospho is a phosphoric acid based rust reformer.  This product converts the rust from iron oxide to iron phosphate, an inert substance.  When using this product, good ventilation is necessary as hydrogen gas is released during the chemical reaction.  I let the Ospho dry for 24 hours and then applied a second coat of it.
3. Now it is time for the Macropoxy 646.  Macropoxy is a 2-component poly-amide epoxy coating.  This coating is not user friendly and should not be used by someone who isn’t experienced with industrial coatings.  Atlanta Painting Pro Hint: Wear gloves and eye protection.  If using this product indoors, a respirator is a must.  This stuff is hard-core.  You must read your data sheets and follow ALL manufacturer instructions when using this product.

• First shake part A and part B.  Then mix equal parts of A and B into a 3rd container (1:1 ratio).  Mix this for about 5 minutes with a mechanical mixer.  Now you MUST wait 30 minutes for the product to sweat.  After 30 minutes, stir the macropoxy and get to work.  You have 4 hours pot life at 77 degrees F with this product.  A pot life is how long the epoxy is workable, after the pot life is over the product solidifies and is finished.  Clean your brush and tools using reducer 15.

Again, I must emphasize that this product is extremely aggressive and should not be used by DIYs.

GOOD LUCK!