Hot dip vs cold spray and epoxied value

[Eric Sedletzky]

That one hole at the bottom of the skin tight boots used on OMS Faber tanks isn't for draining water, it's an air hole so the boot will slide on. Those glove boots being that they were a full contact snug fit were never designed to drain like the veined boots that have ribs inside. Drilling a million holes in the bottom won't cure it, it will just rust wherever there's no hole, like on the sides.
I cut the one boot down on my LP 85 on the sides to only about 2" tall so I can slide it off easily to rinse it. I only use the boot as a tank stand.
That tank is 7.01" diameter so kind of an oddball. I can't find a draining boot to use on it.
What about bedliner? Anybody try that?

 

[Ares1590]

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.

This was a fantastic write up and exactly the information I was looking for. Thanks very much for your time and for your thorough explanation!

 

[Scared Silly]

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.

"Nothing is foolproof to a sufficiently talented fool"

"If you make something idiot-proof, someone will just make a better idiot."

Don't tell your customer the above.

 

[runsongas]

@Eric Sedletzky 7" ID thick wall pvc pipe. cut to length and dremel a few drainage ribs

 

[Belzelbub]

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 don't see HDG tanks getting cheaper any time soon. Currently all my steel tanks are HDG. Got most of them used, and got a ridiculous deal on a couple of them.

I've also previously owned a pair of painted steel fabers. I got rid of them because I wanted to go to a single diameter. The paint they used was pretty robust. Apart from the paint removed during the hydro stamping, there was no other missing paint. They were cared for, but weren't babied. If you are OK with doing a little bit of TLC, I wouldn't worry too much about painted tanks.

 

[Bearded Diver]

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.

As someone who is an aspiring cave/wreck diver, May I ask why the LP 85s are not desired by the vast majority. Weight characteristics/too big/not big enough?

Thanks in advance.

 

[Bearded Diver]

L

Last week at Aquarius in Monterey
View attachment 883090
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.
View attachment 883093

Looks slick!

 

[Bearded Diver]

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.
View attachment 883067
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.

Dang, that cyclometer is rough!

 

[Bearded Diver]

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.

View attachment 883041View attachment 883042View attachment 883043View attachment 883044View attachment 883045

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.

Rough looking tanks. I like removing the boots post dove at one and let dry overnight.

 

[mr_v]

As someone who is an aspiring cave/wreck diver, May I ask why the LP 85s are not desired by the vast majority. Weight characteristics/too big/not big enough?

Thanks in advance.

What configuration did you have in mind? LP85 cave filled are quite popular in Cave Country.