Painting steel tank

[WD8CDH]

For a conventional light weight SCUBA tank, it's hard to beat a 3442psi 80, but if you need a little lighter, here is my favorite light weight single steel tank:

Faber 71 Cubic Foot High Pressure Steel Tank FX Series FX71DVB with reviews at scuba.com

 

[jtpwils]

Can you still read the hydro and other stamping after a powder coat?

Now THAT - I hadn't thought of and may well be a good reason not too.

 

[Puffer Fish]

Can you still read the hydro and other stamping after a powder coat?

Here is a good paint choice:

acrylexpaints

Well, Faber's are power coated, and they can be a bit difficult to read.

About all that one can tell from that web site is that they use an acrylic, water based coating.. not sure what the performance is, but I doubt it is for salt water exposure.

It is important to understand that powder coating, by itself, is not that good for just coating steel tanks.. it is hard... it is moisture resistant, but it does nothing to stop corrosion once it starts from a nick or scrap. That is why Faber uses a zinc coating under their white powder.

There is, by the way, a zinc rich powder coating that can be applied under a powder coated top coat, and there is a way to minimize the heat exposure..

If you look at a salt water trolling motor, the black or white finish on there is a zinc rich primer (melted, but not cured), with a urethane powder coating over the top... that mix is several times better performing than what Faber uses..

Note: I know, because I am the engineer that designed the coating package and application system.

It had to pass 3,000 hours in a salt spray booth, with a scribe line and no rust...even a hot dipped zinc coating will not pass that test.

Only problem is, I don't know where one can buy the primer in the retail world..

 

[Puffer Fish]

Now THAT - I hadn't thought of and may well be a good reason not too.

Just highlight the numbers after you are done...

 

[Gilldiver]

It had to pass 3,000 hours in a salt spray booth, with a scribe line and no rust...even a hot dipped zinc coating will not pass that test.

Only problem is, I don't know where one can buy the primer in the retail world..

3000 hrs of ASTM B117 with no rust? Even chromated epoxies can't do that, MIL-PRF-85582/MIL-PRF-23377 epoxies are good for only 1200-1800 hours.

 

[Puffer Fish]

3000 hrs of ASTM B117 with no rust? Even chromated epoxies can't do that, MIL-PRF-85582/MIL-PRF-23377 epoxies are good for only 1200-1800 hours.

I know.. the coating is 70% zinc...the epoxy resin used to hold it together acts as a reaction rate reducer (resistor if you will) that slows the galvanic reaction rate.

The product was invented for coating transformers used in south florida.. where high heat, salt air and large temperature swings cause normal coating to fail, including galvinized, with a powder coating topcoat. We tested both hot and cold zinc, and while it did great for the first 2,000 hours, after that, the zinc was gone.

We tested out to 4,500 hours (for those that don't keep track of this sort of thing.. that is roughly 9 months.. and you do get a red line at something pass 3,500 hours.

I will bet several million motors have been coated with this process.

Note: I would feel bad about making the above post for being a bit too technical, but I am just responding to Gilldiver's Mil spec post.

Note2: Chromated epoxies don't go 500 hours without some rust on the scribe line.

Note3: The worst salt water corrosion is cause by salt exposure in air... the under water part is easy.

 

[chrisc]

Now THAT - I hadn't thought of and may well be a good reason not too.

Yes there is no problem reading all the info on the tank.

 

[chrisc]

That would be a very bad idea...powder coatings (the normal application method) using very high heat to melt.. not a good idea for a tank.

Depends on the powder. I had ours done with a low heat 130-150 range, bake time was longer too. Process and cost was more, but turned out great.

 

[WD8CDH]

That would be a very bad idea...powder coatings (the normal application method) using very high heat to melt.. not a good idea for a tank.

Whether it uses too high of heat or not, many dive shops wouldn't fill it because they THINK it may have used high heat.

 

[Puffer Fish]

Depends on the powder. I had ours done with a low heat 130-150 range, bake time was longer too. Process and cost was more, but turned out great.

Well familiar with them...that is in C by the way. They are perhaps better than most liquid coating.. but don't have the same performance characteristics as the higher temperature stuff.

Using High Intensity IR, one could use any powder one wanted and not hurt a steel tank.

The perceived "problem" is perhaps the biggest issue.