Hot dip vs cold spray and epoxied value

[Ares1590]

With the discontinuation of faber hot dip tanks, they are becoming very hard if not impossible to come by (especially where I live where scuba and steel tanks are not common), I am curious if they are worth the price bump over spray galvanized and painted steel tanks.

I can get new painted steel around $330 for a LP85 but for a hot dip LP85 it is about $410-420.

I’m not familiar enough with steel tank types to know if that price difference is worth the benefits of hot dip or not.

 

[tmassey]

I'm a huge fan of hot-dip-galvanized tanks. I'm a pretty big *opponent* of painted tanks, *especially* steel tanks.

However, the Faber epoxy tanks aren't really "painted". You can read about it in more detail, but it's a galvanized/epoxy/clearcoat process. It's *very* durable.

Objectively, the tanks are probably more attractive than galvanized, and I haven't seen any evidence that they are less durable. Now, I'm a cave and Great Lakes shipwreck diver -- that's all fresh water. I don't have personal experience with extended saltwater exposure on those tanks. But if it were a problem, I think we would have heard about it by now...

Also, while I'm a very big fan of galvanized, I'm also cheap. So I will -- and have -- paid a premium for galvanized tanks. But not *that* much of a premium. I think I paid 10-15% more (like $50) last time I bought new tanks. There's no way I would personally pay a 30% premium for galvanized.

And if you're not able to buy new galvanized, I would suggest you try to find used tanks, galvanized or epoxy. In which case you'll pay even less for those epoxy tanks.

Unfortunately, you picked the hardest tanks to find on the used market: LP85's. (Well, LP50's are probably harder to find, but most people don't have a use for those tanks anyway.) So you're probably stuck buying them new unless you want to wait a while -- possibly a long while.

But the short answer to your question: HDG is probably slightly more durable than epoxy, and has a longer track record. However, the track record for epoxy is decently long and certainly plenty good enough. So those slight advantages would not, in my opinion, deserve more than a minor increase in price, and I would not hesitate to buy epoxy tanks because of quality or durability issues.

 

[Eric Sedletzky]

Painted tanks are fine, you just have to be careful with them. The other thing with painted is you want to pull the tank boot off often and don't let osmosis get through the paint and start causing problems. I scored a free OMS painted tank (LP85) that was badly rusted under the tank boot. They figured it was no good. I stripped it, bead blasted all the rust out, and epoxy primed it. Then sent it to hydro which it passed. Then I painted it with shiny top coat. The inside was cherry.
The technology of epoxy primers are really good, they provide a barrier coat that is
water proof and oxygen proof. No oxygen, no water, no rust.
But you don't want to go dropping the tanks around on a rocky shore and chipping the finish. Even polyurethane paint systems aren't totally chip proof.
HDG is the most durable, but if we can't get them anymore then no use worrying about it.

 

[Tanks A Lot]

From my experience, the hot-dipped galvanized cylinders are vastly more durable than their zinc sprayed, often called cold galvanized, counterparts.
Simplifying a bit, cold galvanizing works by heating up the zinc only and then applying it as a spray. Hot-dip galvanizing works by heating up both, the zinc and the cylinder. The hot-dipping leads to a metallurgical bond between the two alloys, which is very hard to break. The spray on the other hand works very similar to a layer of paint, meaning it can chip off under certain circumstances. It's not quite fair to compare it to a layer of paint, as it is a bit more complicated.

The pictures below are all of Faber cylinders only.

The damage you see all had user error at its root. Under normal circumstances, the zinc spray is plenty durable. However, leaving cylinder boots for years on end filled to the top with moist sand on the cylinders will cause damage. Equally, sharp hits or impacts can lead to the zinc layer separating from the base alloy.
This is not to say that these cylinders are not durable, they are incredibly tough. But they are not as tough as their hot-dipped galvanized cousins. From an engineering point of view, they can't be, as one bonding method is vastly superior to the other.

For damage to occur, you have to break the paint layer, the epoxy layer and the spray zinc layer. This is hard to achieve, but I'm always amazed by how "inventive" my customers have been in breaking their gear... Crucially, they seemed to have a harder time damaging their hot-dipped cylinders.

In my opinion, other companies such as ECS or Vítkovice got the zinc spray a tad better down than Faber, but their design choices or alloy composition is behind Fabers.

 

[runsongas]

for personal tanks, the faber painted tanks survive just fine if rinsed well after use and the crappy boot they usually come with is replaced

for rentals, i can see why you want the more idiot proof option with hot dip

 

[happy-diver]

The pictures below are all of

quite old with a completely different coating system, with no comparison to todays hardy Faber coating systems

Faber cylinders only.

 

[tmassey]

The pictures below are all of Faber cylinders only.

quite old with a completely different coating system, with no comparison to todays hardy Faber coating systems

That is a point worth repeating.

The current Faber coating process is different than the older process. That’s why I’m careful to call them epoxy tanks, *not* painted. Painted tanks are awful. OMS-branded Faber tanks are well known for rusting. The yellow is a dead giveaway: the epoxy has never been made in yellow but was common for painted. The white is harder to tell apart, especially in photos, but you can tell the difference: the epoxy is thicker and just less attractive. Paint is pretty, but it just doesn’t work.

Also, I should add that almost all of mine are used as doubles, and I take the boots off. If you notice, most of the damage — and certainly the worst of the damage — is where the boot is. Faber boots are tall and almost glove-like, and the bottom only has a single relatively small hole in the bottom. They do a great job of trapping water and holding it against the steel, which is the last thing you want. I recommend getting rid of those boots — or at least drilling several large holes in the side and bottom.

So, yes: I personally would avoid those early OMS/Faber tanks. I’m not sure when the switch was made, but I think it was in the neighborhood of 2008 or so, and maybe a bit earlier? Of course, that’s not relevant with new tanks: they’re all epoxy now. Of course, I did mention used tanks and should have added that information…

 

[Tanks A Lot]

I would have to go back to notes, but I'm fairly certain that some of the pictures above are already from later Fabers. This one however I know to be from a 2016 Faber (16 0294 080), as I noted the serial number on the picture.

There is no doubt that the above cylinder has been heavily abused. It is not Fabers fault for people treating cylinders this way.

I have had one customer that has a fleet of Fabers from 2002, 2004, 2005, 2007, 2008, 2015, 2016, 2018 and 2022. Yes, there is a clear difference between the painting techniques and durability. However, even the newer ones are a long-shot away from being as durable as the hot-dipped galvanized cylinders. I have not seen a hot-dip layer chip off. Sure, it gets removed by scratches, gauges or abrasion, but it generally does not separate from the base alloy.

The epoxy coated cylinders however are able of having the top coat paint, epoxy primer and zinc layer chip off when struck unlucky enough. It is common enough that I had to advise customer to not load their steel cylinders into a small tender before loading the aluminium cylinders. With the steel cylinders laying at the bottom and boat crew throwing aluminium cylinders carelessly on top, I have seen this damage a plethora of times.

Again, I'm by no means knocking Faber, they make one of the best steel cylinders, especially design wise. But the hot-dip galvanizing has a metallurgical advantage that just can't be reached by current paint technology.

 

[johndiver999]

I also would avoid the painted tanks in saltwater if possible. One thing that I have found with the faber tanks is to remove the rubber boot, and drill about 20 small holes all over the bottom of the boot. the single central drain hole that the boot is made with is insufficient to allow the tank bottom to dry and to drain and I think it holds salt water which is very destructive.

I try to always blast the garden hose down the outside of the perforated tank boot after each dive day, and you can see the water leaving the holes. I have much less corrosion under the boot with my painted faber tanks. I do the same with the galvanized ones. It only takes a minute to drill the holes in the boot and it is always worth it, to blast the valve with freshwater after a dive anyway- so shooting water into the edge of the boot is not that tiresome.

 

[lexvil]

Last week at Aquarius in Monterey

HP 100’s, pricy but plentiful took the pictures but didn’t ask about them because the place was busy as heck so got our fills and went home. I don’t know if they are HDG or galvanize painted because when new this is how HDG looks. My 5 will last as long as I’ll be able to dive I think but if I were buying more like the OP’s post I would buy painted ones and put the $ saved toward a 3rd tank. When the paints needs a refresh you can make them any color you want.