|
|
Post by seakrakken on Dec 16, 2004 15:43:07 GMT -8
Can anyone tell me please if nichol plating the inside of steel tanks is accepted by scuba shops for VIP and Hydro? I'd like to buy a steel tank and have this done to it to reduce the rust factor. Why didn't the manufacturers just do this to begin with?
|
|
|
|
Post by SeaRat on Dec 16, 2004 22:52:27 GMT -8
I don't think nickel plating is an easy process for the inside of a scuba tank. Plating on the inside would be tremendously more difficult than doing so on the outside of a tank. If it can be done at all, it would be very expensive.
Also, it probably is not a wise thing to do. A number of people have, or would get, a nickel allergy (some cannot wear nickel-plated rings for this reason). A nickel allergy to the skin is one thing; having the lungs involved in an allergic response is quite another, and could be life-threatening.
This type of allergic response of the lungs is what keeps ex-painters from ever again being exposed to diisocyanate-based solvent in paints.
If you are that concerned about steel corrosion, then switch to aluminum. While steel corrosion is an accelerative process (rust progresses quickly to destroy a tank), aluminum is a self-limiting process (the aluminum oxide inhibits further aluminum corrosion).
The best way to limit corrosion in steel tanks is to use only clean, dry air (or nitrox) in the tank, and keep pressure in the tank. Don't ever let sea water get inside.
John
|
|
|
|
Post by seakrakken on Dec 16, 2004 23:16:03 GMT -8
Thanks very much. I didn't know about the possibilty of an adverse reaction to nichol. I've learned something ;D
|
|
|
|
Post by nemrod on Dec 17, 2004 0:07:16 GMT -8
Not sure about nickel but chrome plating of some steels can cause them to become brittle. I would have to do some looking in my manuals but I think this might apply to nickel as well.
Didn't they used to epoxy coat or plastic coat the steel tanks. I bought a steel 72 about 1966 and it is still in service with little rust. I bought another about 1974 and it failed a hydro due to rust, so I was told. Nemrod
|
|
|
|
Post by Mistral on Dec 17, 2004 5:14:57 GMT -8
Plastic coating on the inside of steel tanks used to be popular in the early to mid 70's and it did prevent rust - for awhile. However, the coating eventualy developed pin noles that then allowed water to contact the steel tank and worse, pretty much trapped it there. This then tended to promote the development of pits in the tank that would eventually result in the tank being condemned.
A coated tank will not (or at least should not) pass a VIP until the coating is removed. Removal takes about a week of tumbling and many shops won't bother with it.
Flash rust in a steel tank is common and is not a big deal. In normal service the tank will need to be tumbled every 5-10 years to remove flash rust if it builds up enough to potentially obscure the walls of the tank or if there is rust anywhere on the tank that may be thick enough to indicate the possibility of a pit.
A pit in a tank is a fatal flaw and will result in the tank being condemned. However for rust to pit a tank, it requires liquid water in the tank or several years of disuse and neglect.
I have 20 some odd steel 72's from the late 60's to mid 70's and all pass hydros and VIPs with no problems. We also see welding tanks come through the shop for hydro from around 1910 that are still in service and pass inspection.
In short, a steel tank will last a lot longer than the owner as long as it is given proper care and periodic inspection so there really is no need for an internal coating and attempts to coat tanks internally have caused more problems than they resolved.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Dec 19, 2004 8:54:09 GMT -8
I wonder too if plating of tanks does not cause some of the same concerns that galvanizing of pipes raises,when they are used for natural gas, that is flaking and subsequent plugging of valves and regulators. Before electroplating, metal would need to be cleaned, and rust removing chemicals are not permitted in breathing air tanks. Not worth the trouble. John
|
|
|
|
Post by Michael on Dec 21, 2004 9:47:59 GMT -8
Plating of any type inside a tank would be difficult at best due to the roughness of the surface. All the other reasons stated above also are valid.
I have had my twin 38's plated with nickle on the outside for corrosion resistance, couldn't find a galvanizer who would do them. The tanks passed hydro for the last ten years since, the last time, 04, the + rating was reinstated. No problems there with outside plating apparently.
|
|
