What is this Metal and What Type Primer to Use?

I would at least consider getting it powder coated, if it's in good enough shape...I think most aluminum patio furniture is nowadays...it's a much more durable finish, a little pricey, but will last longer and increase the value....

Wow, $30 for a pint, $40 for a quart. Ouch.

Interesting. I had considered going to https://www.sanchem.com/ and getting either their iridite kit or the very fast iridite-like surface prep kit. I have used both in the past and been happy with both results and the fact that their solutions are 100% EPA safe and legal do dump down the drain. Even though $30 is a little painful that is probably what I would pay for shipping from San Chem. This might not turn the metal golden in color but it might be creating the same conversion coating.

Thank you.

This can be used directly to prep the surface before priming and painting.

See the datasheet for more instructions. It is slow-drying so it will penetrate well.

http://buyat.ppg.com/rep_pafpainttools_files/Flood/tdb/FB_FLD4_USEN_021116.pdf

Recommend gently wire-brushing off any loose stuff first. The instructions state to use steel wool saturated in the Penetrol to apply to metal surfaces.

Then you can mix it with your oil-based primer and top-coat to improve adhesion and flow into all the fine details of your bench.

Good luck with your quest.

Interesting. After reading the data sheet twice I'm still not sure what it does. Some of the text seem like a thinner to allow the paint to soak in better and delay drying time. Some of the text seems to be saying something different. Have you used it?

The data sheet says your materials will spontaneously catch fire. That does sound like fun. You know a product is "old fashioned good" when birds that were flying by drop dead out of the sky and the item you are working on self ignites and burns. Add in a little energetic disassembly and we could have a party.

Sorry, sometimes you can tell I don't have adult supervision. Thank you for the suggestion.

I've used it directly on old weathered wood that just wouldn't take paint. Soaked in and once it dried (takes a while like linseed oil) then the paint would stick. I'm not sure what's in it. I seem to recall that rags soaked in linseed oil can get hot too, so maybe it is a similar to linseed oil.

It could be cast aluminum (if it's not heavy) or "white" metal (scraps of different metals melted together).

The corrosion is odd looking to me. As I flake off paint there is a uniform white corrosion layer extending from the exposed areas to the areas under paint. The base metal under the corrosion is rather uniform. As finishes fail on aluminum I usually have seen more of a "I'll dig in here" and "I'll dig in there" sort of miniature canyon corrosion damage to the surface.

I'm sure I have had things that were a zinc alloy casting but I have never had anything that I was confident was a zinc casting. My experience with zinc corrosion has been either a coating that weathered through after a decade or a galvanized surfact that corroded after I left it in contact with a dissimilar metal. Neither one of those seems similar to this.

About a year ago I did some research on painting a galvanized surface. Several references indicated that if everything wasn't perfect the zinc would corrode under the paint and the paint would fall off. I can't help but wonder if that is what is happening here.

Past experience as QC/QA Manager for Houston's largest furniture powder coater tells me that in all likelihood it is cast aluminum. (FYI: cast aluminum is a lot more porous, less ductile and weaker than standard sheet rolled ingot aluminum.) The "white stuff" is oxidized aluminum. If you paint use a drill or angle grinder mounted wire brush to give a fresh and clean surface, then use any good automotive primer and top coat. For a 10-year solution have it powder coated (FYI #2: A good furniture coater will, as part of their standard practice, replace the hardware with stainless and put new nylon foot pads on it.)

In the past I have refurbished some of these in tables and chairs. It is likely the seat is an aluminium of low quality, maybe the melted down alloy heads of Tojo cars and I have encountered the white oxide often. I usually hit it with a degreaser containing a weak sodium hydroxide content, too strong and you will make hydrogen, good for balloons and fireballs. Next after it fizzes a bit I use a power washer to get it really clean.

For painting I would use an etch primer especially for Aluminium sprayed in a couple of thin layers allowing it to flash off between coats. Follow the instructions as to drying time as in a moment of eager exuberation I applied the top coat too soon and it crazed sometime later.

When dry I use an automotive enamel or if you are really flushed with cash you could use a two pack auto paint. Originally the paint has been applied with no undercoat just a top coat so the moisture gets under the old paint and corrodes the metal.

This will do well,I think:

https://www.caswellplating.com/yellow-chromate.html

Chromate conversion surface finishes are always good. Thanks for the suggestion.

You ask what is this metal?

You should be able to distinguish between aluminum and the other common white casting metals with a scratch test. Aluminum oxide will scratch glass. Some grindstones are made of aluminum oxide, as are some sandpapers. I'm pretty sure that the oxides of the other white metals like zinc are too soft to scratch glass.

The fluffy white corrosion seems soft but I question being able to trust that observation. I would think that 1200 grit (and higher) aluminum oxide would also seem soft to the touch if instead of being bonded to paper/cloth it was loose and clumped together by having previously been wet.

I agree on the "fluffy white stuff". I assume that your pen-name here on CR4 implies that you live in Florida, where the humidity is high and there is a likelihood of salt in the air. This lends credence to the idea some else mentioned of it being efflorescence, or a combination of aluminum oxide with efflorescence (which could include sea salt and one or more aluminum salts).

I wrote the suggestion of a scratch test simply from previous knowledge, without doing any experimentation. This morning I did a little experimentation: I simply rubbed a clear glass beverage bottle on edges of several samples of different metal objects. To my surprise, a piece of 6061 Aluminum that was machined several years ago did NOT scratch the glass. The only item I found that did scratch the glass was an aluminum drain grating that was heavily oxidized and rough after years of use/storage outside.

This does to some extent verify my hypothesis...

Central Florida is correct. I am about 2000 feet from the ocean so I only notice salt when there is a strong wind coming in but at a corrosion level I probably get salt every day.

The material is likely a zinc aluminum alloy. The white powdery surface is typically zinc oxide and/or aluminum oxide. You would need to bead or sand blast the metal to remove the oxide and then use an aluminum primer, though I would personally go for an epoxy finish or possibly a good sealed powdercoat. If you leave any of the oxide on the metal, it will propagate. If you have pores in the finish, the metal will oxidize, swell and push off the finish over time.

not at all trying to be confrontational, so please do not get offended with my questions, i am trying to learn more.

So if one has a coating that wets the oxide surface and is hermetic, then removing to bare metal should not be needed correct?

if you have pores in the finish, it would not matter if you had oxide or not? what am i missing? maybe the oxide is a lower pH, causing more corrosion??

i guess i do not see why the oxide causes more of an issue than bare metal if the coating wets it properly.

thanks.

No offense taken.

The oxide specific volume is much greater than the base metal, so when it forms it expands, peeling away an applied finish. The oxide also has negligible strength. If you apply paint to the oxide, then in a relatively short time you have a bag made of paint containing loose powder that wraps around a floating core of base metal.

Concerning removal of the oxide, the material retains free oxygen, hydroxides and a certain percentage of hydration and free water that will continue to attack the base metal. The aluminum/zinc oxides and hydroxides do not form a passivating barrier to further corrosion.