Atomic ST1 Does it rust?

[dingopauly]

Hi All
I just took the plunge and ordered a new Atomic ST1, I was swayed by the excellent reviews and the idea that the stainless 316 is stronger lighter and more corrosion resistant than chromed brass.
Now I have done a little more snooping around and found a great site with lots of info about stailnless 316 it was Very informative about the properties , but I was disturbed to find this paragraph in the Corrosion resistance heading.

316 is usually regarded as the standard “marine grade stainless steel”, but it is not resistant to warm sea water. In many marine environments 316 does exhibit surface corrosion, usually visible as brown staining. This is particularly associated with crevices and rough surface finish.

Has anyone out there had problems with staining? would be particularly interested to hear from pro's who use this on a daily basis.
Thanks.

 

[Scott L]

I just purchased three of them. The design and quality of machining/manufacture is second to none. I am very confident that they will not suffer from any of the issues raised. If not, I would like to hear the reports...

 

[BDSC]

Under the conditions that you will use this product you will never see any rust or corrosion. 316 has been used for years in coastal environments because of it's properties with only occasional rainfall to wash away the salt spray/air and it will last for years without any signs of corrosion.

Great purchase by the way. I was going to buy an ST1 myself until I found a T2X that had only been on two dives for about half price.

 

[fnfalman]

Stainless steel is not rust proof. Rust resistant but not rust proof. The ST1 would probably take a bit more negligence than chrome plated brass but it will rust if abused or neglected long enough.

 

[Akimbo]

As you have probably read, austenitic stainless steels themselves are not especially corrosion resistant. It is the corrosion process itself that forms a micro thin layer of chromium oxide that protects the base material. This protective layer is generally "self healing", meaning that scratches to the chromium-oxide layer will quickly repair without visible scaring.

This is the same process that protects copper based alloys and silver. However, the result on stainless is much thinner, harder, and visually indistinguishable from the base metal. I understand that this explanation is a simplified summary that would not satisfy a metallurgist, but is close enough for the rest of us.

One of the factors that can interfere with the formation or repair of this micro layer are ferrous particles, either from the manufacturing process or imbedded during use. The most common method of preventing this unsightly surface and minor pitting is call passivation or pickling. Basically, a solution dissolves the ferrous particles so they don't interfere and discolor the chromium oxide layer.

Here is a good article and procedure.

How To Passivate Stainless Steel Parts : Modern Machine Shop

There are services that do passivation but generally are not interested in vary small lots or private individuals. People who work with stainless a lot maintain a separate set of non-ferrous tools, cutters, and abrasives to prevent contamination. I can't personally vouch for Atomic Aquatics manufacturing procedures, but I seriously doubt you have anything to be concerned over. Their reputation for quality control and customer service is impeccable. That is one of the reasons their products are able to command a premium in the market.

 

[dingopauly]

Ok thanks for the feedback.

 

[Couv]

The complaints I’ve heard re stainless steel first stages was not about surface corrosion. The problems are associated with the mating surfaces of two parts. Apparently corrosion can form between two parts making them a bugger to get apart.

c

 

[Akimbo]

The complaints I’ve heard re stainless steel first stages was not about surface corrosion. The problems are associated with the mating surfaces of two parts. Apparently corrosion can form between two parts making them a bugger to get apart.

There are two characteristics of stainless that are probably at work. The surface oxidation already discussed is often damaged by the friction on threads, especially when rotated against a force — like a spring. Probably a bigger problem is the tendency of 300 series stainless steels to gall.

Stainless Steel Galling / Locking Up / Freezing Up

In my experience, thread galling on stainless is particularly severe on tapered pipe threads. It is not uncommon for tapered threads to seize so badly that the fittings are broken off and threads remain locked. Unfortunately, just because these joints are hopelessly seized, they usually are also leaking!

I have heard a number of theories including those described in the link above. I personally suspect that there is also a characteristic of stainless to raise micro burrs that act as thousands of tiny one-way stops. I have seen times when I could not unscrew a stainless threaded connection, but I could tighten it a little. I have also noticed that galling of machined threads is much more frequent than on rolled threads.

Stainless is often described by machinist a "gummy". Stainless is softer than most steels and has lower thermal conductivity, which may account for this complaint. One thing for sure, cost of machining stainless is much higher due to lower material removal rates.

Galling is such a big problem that we always avoided screwing a stainless steel taper pipe fitting into stainless steel penetrator — couplings welded into pressure vessels like chambers, bells, volume tanks, etc. A damaged penetrator can take a chamber out of commission and cost thousands for repair if the chamber had to be welded and re-hydroed. Usually they just tig weld the fitting to the penetrator and work around it.

 

[dingopauly]

I just have to add, my reg arrived today, and it is a work of art! Beautifully made, can't wait to give it a go.