Barrier coats & sealants for concrete & steel

Ulu

Giant Snakehead
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Dec 13, 2018
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The Sunny San Joaquin
For reinforcing steel in concrete, in seaside projects, epoxy-coated steel is always specified.
I would definitely epoxy-coat any metals in contact with concrete, before installation.

Then touch up any welds, wire ties, stirrups etc. after the cage is in place, but before pouring concrete.
You want to make sure you have 100% coverage of the steel.
Same with the angles.

Look at the forensic history of reinforced concrete and salt and you'll see why.

Or visit Alcatraz Island for a good look at what happens when the steel rusts and all the concrete just falls away.
That takes time, but it is inevitable.
 
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fishdance

Piranha
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Jan 30, 2007
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Something else to consider; I placed some sacrificial anodes in my freshwater tank to galvanic protect the steel frame. Very similar to how they protect metal boats and propellers but with magnesium not zinc (freshwater).

Probably not worth it on a smaller tank but I considered it to be cheap insurance in my situation. I've got a 1.5m long rod at each end of steel frame. You can't see the rod through the viewing panel.
 

Ulu

Giant Snakehead
MFK Member
Dec 13, 2018
1,361
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The Sunny San Joaquin
Something else to consider; I placed some sacrificial anodes in my freshwater tank to galvanic protect the steel frame. Very similar to how they protect metal boats and propellers but with magnesium not zinc (freshwater).

Probably not worth it on a smaller tank but I considered it to be cheap insurance in my situation. I've got a 1.5m long rod at each end of steel frame. You can't see the rod through the viewing panel.
This has been tried on buildings, but it's not quite so effective as on a ship hull. Much attention must be paid to bar connections, to make them electrical connections, where normally they are just tied with wire, and not solidly at all. The concrete normally provides the solid physical connection. The wire is just for setup, until the concrete hardens. On a fully welded cage, it would probably be just fine until the anode vanishes. Some cages use crimped or threaded connectors, which could prove problematic.
 

fishdance

Piranha
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Jan 30, 2007
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Sacrificial anode is not necessary but very cheap insurance. It would work well in a water tank as this is simply a ship filled on inside. The anode needs to be monitored and replaced as needed.

Sacrificial anodes aren't as effective on buildings or vehicles as these don't have water to complete the electrical (galvanic) circuit but those can be boosted by battery.

Anyway getting off topic.
 

andyroo

Jack Dempsey
Original poster
MFK Member
Apr 17, 2011
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MoBay, Jamaica
www.seascapecarib.com
* Neoprene for the same reasons as we set styrofoam under an all-glass: that is wise... though finding bare neoprene sheeting on this island's going to be a drama. Alternatives? VERY thick silicone bead? ;) What is this plastic spacer-block you speak of?
* I'll ask about Admix. Appreciated re. pH curing/calming fairly quickly. It'll be rainwater filled and rainy-season should coincide with the fill dates so can flush-flush-flush.
* 6cm of glass-steel overlap is a lot- I'm looking at just the 1.5" (just over 3cm) of the angle-iron for this "smaller" tank. Do I need to re-think?
* I'm not sure what you mean about the spatula for the silicone- to jam it down into the gap to drive the material in & around the corner? Ok, I can do that.
* West System's responses have been wishy-washy, suggesting I set 5coats to get a waterproof seal. Screw that - I'll get the purpose-built Dulux that you suggest, which sounds familiar so may not need to import. Let's see...
* I've used Aluminum bar as non-toxic martyr anode before- highly noble so works like a charm, but gets crusty & needs regular cleaning. Magnesium is better in that regard.
Thanks,
Andrew
 

fishdance

Piranha
MFK Member
Jan 30, 2007
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I don't think you will need anything but a wide silicon gap/bead on a 34 inch deep tank. The spacer block is to get a uniform gap and to ensure the water pressure couldn't push the glass directly against the steel. It's important not to push the glass too close and pull back as silicon is squeezed out then vacuumed in with bubbles. Use a neutral cure silicon so you can remove the spacer (shim) and fill with silicon a day later with silicon bonding. I only used neoprene for UV resistance and compression. I only used 60mm overlap because my glass sheets were large (60mm thick) requiring a crane to install so I engineered for a simple placement

The dulux protective barrier is used for commercial applications. Impressive specs but I'm sure other brands would work.
 
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