External rust, stripping & painting steel tanks

Discussion in 'Tanks, Valves and Bands' started by Fishkiller, Jan 19, 2002.

  1. Fishkiller

    Fishkiller Manta Ray

    # of Dives: 100 - 199
    Location: Mesa Arizona, The all beach no ocean state.
    1,169
    1
    0
    I was looking at my plane white LP121 steel tank and thought hey paint it like a Watermellon, get it O2 Chicken cleaned and use it for a EANx tank. I will just go down to the store and get some spray paint and tapeto give it a two tone design, then give it a clear coat over it all.. Now the question is do I need to have it hydro'd again??
     
  2. Rick Murchison

    Rick Murchison Uncle Ricky Staff Member ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: Gulf of Mexico
    13,298
    508
    113
    There are two issues with paint on tanks.
    (1) Paint hides stuff. Realize that any time you paint you potentially provide an area for undetected rust or corrosion. Not such a big deal with AL tanks, but some serious rust can grow under paint on steel. For that reason use a paint with a rust inhibitor in it - and clean the tanks clean, clean, clean and make sure they're absolutely completely totally dry before painting - and don't paint on a humid day.
    (2) Temperature - many paint processes - especially commercial - involve baking on the paint. This is an ABSOLUTE NO-NO with scuba tanks. It weakens the metal and can and HAS resulted in tanks exploding and killing people during fills. For this reason, fill stations may be reluctant to fill any tank that isn't factory painted with a color they can recognize as a regular factory color.
    Painting at room temperature with epoxy or spray paint doesn't warrant a hydro, unless your prep has involved sanding - sanding the tank warrants a hydro. You may have to get a hydro after painting anyway before the fill station will fill it - the last guy I know of who brought in a baked tank to be filled swore it wasn't, and the tank blew - and most folks in the tank filling business know it. So if they insist on a hydro first even though your paint job is obviously not baked, go on and bite the bullet - after all, it's their tail on the line when they're filling.
    Rick
     
  3. trymixdiver

    trymixdiver Manta Ray

    956
    0
    0
    I need to touch up my tanks. I just got hydros and the new stamps have damaged the paint.

    I want to prime the bare metal first, should i use oil or water based primer ?

    Andy
     
  4. trymixdiver

    trymixdiver Manta Ray

    956
    0
    0
    i gess i should use the same type of paint OMS used, water based or oil based.

    Does anyone know if OMS tanks come painted with oil or water based paints ?

    ANDY
     
  5. schmisl

    schmisl Angel Fish

    13
    0
    0
    To refurbish a steel tank could you sandblast the tank and use Rustoleum cold galvanizing compound paint?
    Anyone ever do it this way?

    Thanks
     
  6. Campana

    Campana Barracuda

    # of Dives: 500 - 999
    Location: Wills Point, Texas
    270
    0
    0
    I would strip it with stripper, clean it up, and paint it. I wouldn't take a chance on losing any material. You might bead blast it or something. Stripper works fine. Then put your cold galvanizing on it and paint it with some good paint. I've got one painted John Deere Green that looks pretty snappy, and a red rustoleum painted one. Actually it's quite easy. I think people obsess too much about painting tanks, just do it.

    As far as cold galvanizing, FredT knows the best kind, but I can't remember. I'll write it down this time. I got some that is supposed to be "marine" but it's pretty lame.

    Now that I mention it, FredT knows about everything, but don't ask him about politics. Really.

    Dave
     
  7. douhunt

    douhunt Guest

    5
    0
    0
    not to be a smart a**, but i would not worry about painting it. It's for diving and its gonna get beat up.

    jusitn
     
  8. Thomas Ivey

    Thomas Ivey Angel Fish

    48
    0
    0
    The OMS product (Faber) uses a two-component epoxy paint. It is my understanding that OMS sales a touch up kit, due to if this area goes un-attended it could develop external oxidation, once this starts it is difficult to stop. I would check with your local OMS dealer.
     
  9. Stoo

    Stoo Loggerhead Turtle

    # of Dives: 5,000 - ∞
    Location: Freelton, Tobermory, Ontario, Canada
    1,378
    753
    113
    I occassionally dive with an OMS 98. The tank is 5 years old, never been in salt water. I have used an OMS boot on it always. I just took the tank in for a visual and learned that the coating under the boot has completely corroded away. Even though the tank hadn't been in water for 2 weeks, there was still a significant amount of water trapped there.

    I sent a note to OMS a couple of weeks ago, but haven't heard back from them... don't really expect too. This tank probably only has about 50 fresh water dives on it and it appears to be toast. It is dissappointing that a company with OMS' reputation hasn't addressed this...

    Has anyone else had similar problems? I generally dive twin Scubapro 95s with boots. These tanks probably have 400-500 dives on them and show no sign of corrosion.

    I also use an OMS 46 for O2. I removed this boot as well and found a large amount of water there as well.

    I know that boots aren't generally a great idea, but I dive from a small boat with fiberglass deck, and I want the boot to protect the boat...

    I'd be interested in hearing from others who have had similar problems...

    Stoo
     
  10. Waterlover

    Waterlover Barracuda

    322
    0
    0
    OMS recently lost a lawsuit over their paint problems from 1998. I have the same problem with 2 98's but they want to charge me to repaint them so I am going to do it myself eventually or sell them and get PST tanks. I just keep touching up the bad spots and peeling the paint as it flakes off....I don't have the link to the lawsuit but it was on Mid Atlantic diver group on Yahoo. Good Luck
     
  11. large_diver

    large_diver Loggerhead Turtle

    2,385
    139
    63
    My OMS 98 is 2 years old and so far no problems.....but I take the boot off after every dive, rinse the tank and boot, and then let the tank and boot dry before putting the boot back on.

    My LDS has told me several stories similar to yours -- "lightly" used OMS tanks with nasty corrosion under the boot. The LDS tried contacting OMS.....OMS ignored them. Now the LDS no longer sells OMS gear.....
     
  12. Stoo

    Stoo Loggerhead Turtle

    # of Dives: 5,000 - ∞
    Location: Freelton, Tobermory, Ontario, Canada
    1,378
    753
    113
    Funny that companies just don't see the connection between lackluster service and declines in business...

    Thanks for the feedback folks. I don't really expect them to replace the tank... so I guess I will... just not with OMS...

    S
     
  13. FredT

    FredT Loggerhead Turtle

    # of Dives: I'm a Fish!
    Location: The remains of the MS Gulf coast
    1,507
    3
    0
    WAy back when on anther board....
    As a side note Luxfer no longer has the same replacement policy for neck cracks.

    FT

    JProsser99 wrote on 4/25/97 rec.scuba.equipment:
    >
    > Seem to have missed the original metal tank coatings post which I did not
    > see listed now. Looks like I missed a good post: can someone forward me a
    > copy of it? Thanx! (jay’s address removed)

    It's available on Deja news archive.

    HTTP:\\www.dejanews.com

    but you _asked_ for it so here goes.

    -------------Start quoted text--------------------

    Carl Heinzl wrote:
    >
    > >Now Carl - what's wrong with OMS tank? I was about to buy one tomorrow.
    > >Seriously!
    >
    > I too was going to buy some OMS tanks before I found out all this. Ok
    > this is from memory as some of this stuff is till put away in boxes.
    >
    > 1) Their buoyancy characteristics aren't as good as pressed steel.
    >
    > 2) I forget what type of galvanizing they do, I think it is sprayed on,
    > but it is NOT hot dipped galvanized like pressed steel (and that is a
    > big one).
    >
    > There was more but I don't remember it off the top of my head. Pick up
    > tanks that are *hot dipped* galvanized though.
    >
    > Perhaps others can expound on this more fully than I.
    >
    > -Carl-

    Carl,

    I don't have an OMS tank and know of no incidents of coating failure (or success for that matter) with them, but I am relatively familiar with coating technology.

    There are 3 commonly used methods for galvanizing in production operations. Normally flame spray is not one of them, but it may be used if there was a concern for the heat treatment of the tank. The normal methods and some of the differences are: (all dimensions in inches)

    1. Hot Dip
    This process involves mechanically or chemically cleaning the object to be coated to bare steel, sometimes preheating the object, and then dipping the object into a tank of molten zinc. The zinc will form a metallurgical bond with the steel similar to a brazed joint where a small percentage of each metal goes into solution in the other forming a bond at the atomic level. The amount of coating remaining on the object is dependent on zinc pot temperature, withdrawal rate and any mechanical removal done as the hot coated object is removed from the tank. Normal coating thickness is often in excess of 0.005". Air knives and mechanical wipers are used on some products to limit film thickness in critical areas. A multiple dip process can obtain heavier coatings in excess of 0.030”.

    ++Hot Dip normally provides the best adhesion, heaviest film thickness, and least pinholes in the coating of any method.
    ++ Pinholes tend to self-seal when in contact with water.
    +Can be done in an automated process on a production line with minimum labor involvement.
    +Process quality control is easy to monitor and has relatively wide acceptable levels for the critical variables.
    -Energy intensive as the entire object must be heated to above the melting point of zinc and the molten zinc must normally be maintained at plating temp round the clock to provide production throughput.
    -Expensive USA EPA and OSHA requirements for zinc fume scrubbing and worker contact can run up the costs significantly over previous years.
    -Effectively prohibits any heat treatment step requiring soaking at or below the zinc pot temperature from being effective. Normal realities involved in heat treatment of steel will usually prohibit engineers from incorporating the galvanizing process into the middle of a heat treatment process following the hot forming of the tank itself since beginning and end of day in process work will have different time constants. This limits material choices.
    -(For the manufacturer) thin films are often difficult to maintain with this process. This uses more zinc and thus adds cost to the product. This heavier minimum coating I consider a + for scuba tank owners. Makes it much harder to get a tank off spec on the thin side.:)

    2. Electrogalvanized
    This is simply an application of zinc to the surface of the steel by the electroplating process. The object to be coated is etched to remove any surface contamination and immersed in a chemical bath with an applied voltage. The coating drops out of solution on the surface to be coated. The bond is normally at the metal crystal and/or surface irregularity level. Normally used where the required coating thickness is measured in parts of a thousandth of an inch to 0.002". Heavier coatings can be obtained at longer bath dwell times but thick (.005 and up) single coat electroplate of _any_ metal has a tendency to bond failure and will often chip off during localized impact. Coating will preferentially be deposited on sharp outside corners and be thinner in valleys. This may be a problem at tank necks. The process is relatively cold and does not limit heat treatment choices. Coating variables include bath chemical concentrations, dwell time, current density per square inch, temperature, and driving voltage.

    +Well understood and developed technology.
    +(For manufacturer) Easy to maintain constant coating thickness with minimal material usage.
    +Can be set up as part of a production line with limited impact to start and end of day work in progress.
    +No constraints on heat treatment/wider material selection.
    -More variables and relatively narrower acceptable bandwidth for quality control purposes. Monitoring equipment is more maintenance sensitive than that needed for HD.
    -Chemical baths often require treatment as hazardous waste during disposal driving up costs.
    -Coating can have unbonded areas not immediately visible on inspection and pinholes do not normally self heal as rapidly as HD, if at all.
    -Chemical baths require a similar level of US OSHA and EPA safety hardware and pollution control as HD.

    3. Impact coating.
    This process involves placing zinc (or other metal powder) in a tumbler along with the parts to be coated and an appropriate transfer medium (ceramic chips, steel balls, etc.) if required and running the tumbler for several minutes up to several hours or days. The coating is applied in a _very_ thin coat by being cold welded to the object by repeated impacts as the parts and transfer media roll around inside the tumbler drum. This process can also provide a limited deburring action. Often used with nuts, bolts and other small solid parts.

    +Minimal material usage as unapplied powder and transfer media can be reused batch to batch.
    +Minimal energy consumption.
    +Time and transfer media wear are the only variables not totally controlled up front. Effectively no problem for quality control.
    -Only relatively thin coatings <~0.0005" can be applied.
    -Applicable to batch processing only.
    -Difficult with scuba tank sized objects.


    4. Flame spray or metal spray process:
    The fourth type of coating is relatively rare in production but has gained widespread use in the maintenance industry for building up worn shafts at seal and bearing points and applying expensive protective coatings or hard surfacing at known wear points on otherwise lower cost items. Shafts and electrical contacts are two applications that come immediately to mind. I see no reason why a scuba cylinder _couldn't_ be coated this way, and a couple of reasons why it would appeal to the manufacturer. As far as the process path goes normally the material to be coated is mechanically cleaned to near bare metal at the start of the process. The process itself involves an oxy-acetylene, oxy-hydrogen, or other high temp torch impacting the surface to be plated and adjusted to provide a slightly reducing (oxygen starved) flame. The metal to be plated onto the surface is powdered and introduced into the base of this flame. Any surface oxidation on the part is removed by reducing any metal oxides on the surface back into the parent metal as the excess fuel in the torch consumes the oxygen from the metal oxides. It's possible to melt or soften the very surface of most metals without transferring much heat to the core of the product by controlling the torch temperature, flame velocity, and time the flame is in contact with any spot on the object to be coated. The coating metal powder is melted by the torch between the introduction point and when it contacts the softened or melted surface of the object and forms a good atomic level bond with it. Coating thickness is controlled by the speed of the torch, amount of powdered metal introduced, and torch path. Thickness can be as low as tenths of a mil (0.0001") up to several inches depending on the material deposited and number of passes involved. The variables in a production operation would normally be tracked by automated machinery and include powder particle size, fuel/O2 mix ratios, flame velocity, distance to surface being coated, powder feed rate, object temperature and cooling, etc. An example of an uncontrolled variable would be any transient jamming in the powder feed tubing. Provided the quality control is tight enough, and the coating is thick enough, a metal-sprayed zinc coating should be about the same as a hot dipped coating galvanized one. The greater number of critical variables in the process and the natural stinginess of production foremen (must minimize costs you know) combine to create a greater potential for coating failure in the field than in HD.

    ++ Good control of coating thickness and thus of costs.
    ++ Minimal USA OSHA and EPA requirements since molten metals and hazardous chemicals are not obviously involved. Fume collection on a relatively small flame spray booth would be about it. No, or minimal, hazardous waste since unconsumed powder may be reused or sold as a by-product to impact or electro-platers and die casters.
    + Frees up heat treat and material choices since sidewall core temperature can be controlled to _any_ reasonable point. It should be possible to limit wall core temp to less than 400F during the process. This will allow use of almost any High Strength Low Alloy or alloy steel for tank construction from a heat treatment point of view.
    -Complicated quality and process controls are required to provide an acceptable product. Process transients can produce thin spots in an otherwise good coating without being immediately obvious.

    The last item is the big kicker! Top management commitment to quality control is MANDATORY for this type of coating to be consistent and suitable for repeated immersion in seawater. Thin or spotty coatings on a few tanks will kill their reputation with the tech crowd. From what you said earlier it sounds like this has already happened. The tech crowd also tend to be a vocal lot with well-formed and entrenched opinions and tend to pass these on to others not of the tech persuasion. Considering that the techies are often opinion leaders in this game it sounds like OMS may have stepped in it big time!

    IMNSHO If OMS has developed this reputation the only saving grace it has open to it would be to match Luxfer's neck crack tank replacement policy with their coatings. As it was explained to me if any Luxfer tank fails a VIP due to neck cracks they will replace it, period. No limitation on number of owners or age of the tank. Ship it to them with the PSI inspector’s paperwork and they'll ship back a new tank! If OMS
    unconditionally stood by their coatings to the same extent no diver would think twice about buying one. If he got a bad one it would be replaced with a new one. No (hard) questions asked. No proof of purchase or other legal nastiness required. For the price of the postage to get the tank back to them with a VIP inspection report a new one would appear at your door in less than a month!

    FT

    BTW Not having ever personally dealt with them I have no idea what their warranty currently is.
     
  14. FredT

    FredT Loggerhead Turtle

    # of Dives: I'm a Fish!
    Location: The remains of the MS Gulf coast
    1,507
    3
    0
    Have them bead or otherwise externally abrasive blasted in the boot area. Rust fluffs way up when it forms so it may look worse than it really is. The actual pits may be small enough to pass a visual. If so quickly recoat the white metal tank with ZRC.

    Not having seen your tanks it may be a long shot, but I have often rehabbed tanks with boot corrosion damage that way. At the very least it won't hurt a garden gong to be cleaned up a bit. Expect the effort to take about 10 minutes a tank to blast, and another few $s for another vip by a PSI inspector. ZRC is about $50 a gallon, which should do several tanks. Given the $s involved in getting new tanks a few $s risked to try and rehab those may be money well spent. Alternately a $10 syphon hose blaster, a bit of beach sand, and a bottle of air routed through your first stage will be enough to do a spot test to see if it's worth pursuing.

    BTW if going the ZRC route clean the ENTIRE tank exterior to bare metal and recoat completely. You already know the coating it has is not suitable for what you want it to do, so you might as well replace it with a good one.

    FT
     
  15. Stoo

    Stoo Loggerhead Turtle

    # of Dives: 5,000 - ∞
    Location: Freelton, Tobermory, Ontario, Canada
    1,378
    753
    113
    FredT:

    Thanks for the insites. I agree that the tank would still pass a visual... for now. I am not familiar with ZRC. Is it a paint of some sort? I am up in Canada, so the stuff might not be available here.

    Your comments about the company's commitment is "right on" as well. If they would even have the courtesy to respond, it would go a long way. I've been diving for almost 30 years and have a basement full of highly "experienced" tanks... all of which are quite useable (the joy of fresh water!)... except this one.

    S
     
  16. FredT

    FredT Loggerhead Turtle

    # of Dives: I'm a Fish!
    Location: The remains of the MS Gulf coast
    1,507
    3
    0
    See :

    http://www.zrcworldwide.com/galds.htm

    As far as I know it's available almost everywhere, at least in "English" speaking countries.

    Surf about on the site for other good info. I've used the stuff for over 20 years. Works GOOOOD where a dip galv can't be done, or to touch up damaged dip galvanizing.

    FT
     
  17. Ray2

    Ray2 Angel Fish

    40
    0
    0
    I've got the same problem with my OMS 85 well maybe .The paint is bubbling up but when I chip this area out to look at it there is no sign of corrosion underneath.Mfg'd in 10-97.Rust does form very quickly on any spot that bare metal exposed and the bubbling seems to be concentrated in the boot area so I check after every dive,salt water only.My PST 95,made in 77 holds up great under the same conditions though.PST may be the way to go.
    Ray
     
  18. Stoo

    Stoo Loggerhead Turtle

    # of Dives: 5,000 - ∞
    Location: Freelton, Tobermory, Ontario, Canada
    1,378
    753
    113
    Thanks Fred...

    Most of us speak English up here... except our Prime Minister Cretien... he doesn't actually speak either of our "official" languages!

    S
     
  19. Goldminer

    Goldminer Nassau Grouper

    87
    0
    0
    This winter I was researching a tank purchase and was considering OMS/Faber tanks. I sent them an e-mail asking about corrosion protection and this is how they responded:

    >It is an automotive-type paint called "IMRON." It is applied in
    >a cold-spray galvanized method.
    >The boots do have a drainage hole, however it is recommended
    >that you wash off your cylinders after each dive. The warranty
    >does not cover corrosion under the boot. That is the diver's
    >responsibility.
    >
    >Safe Diving
    >
    >>-----Original Message-----
    >>From: ----- --------- [mailto:---------_-@hotmail.com]
    >>Sent: Sunday, January 06, 2002 8:31 PM
    >>To: Info@OMSdive.com
    >>Subject: Request for Product Info
    >>
    >>
    >>Dear sirs:
    >>
    >>I am looking to purchase a couple of scuba tanks and have
    >>visited your web site. I saw the following desription of your
    >>cylinders: Corrosion Protection (External): Galvanize & Paint
    >>
    >>I have some questions. Is this hot dip galvanizing,
    >>electroplate or some other method? Also are the boots on
    >>your cylinders drained to help prevent corrosion?
    >>
    >>Thank you
    >>
    >>----- ---------


    No matter how well you look after the tank they don't warrant "under the boot". I came to the conclusion that they don't warrant their product adequately and bought PST.
     
  20. Stoo

    Stoo Loggerhead Turtle

    # of Dives: 5,000 - ∞
    Location: Freelton, Tobermory, Ontario, Canada
    1,378
    753
    113
    OMS' website:

    "Warranty

    OMS Inc. at its sole discretion will repair or replace Ocean Management Scuba Cylinders, proved to have a manufacturing defect, with a service and handling fee of $30.00 per cylinder for a period of up to 180 days from the date of purchase.

    This warranty specifically excludes all warranty claims resulting from abuse, misuse, and neglect including but not limited to internal corrosion, impact and abrasion damage, corrosion determined to be caused by failure to remove the boot...
    "

    I don't remember anything like that coming with the tank... even if I had, I would have ignored it, since the tank is only used in fresh water.

    What surprised me was the amount of water trapped by the boot on the 96 as well as the 46.

    I've been at this for 30 years and have a bunch of old tanks kicking around... all of which are fine. Never removed the boots on any of them.

    I recognize that this is beyond their normal warranty terms, and as such I don't really expect them to replace the tank... perhaps some assistance with refinishing would be nice... Hell, I'd be happy if they would just answer my email!


    S
     

Share This Page