MK25 Rust

[cavesprite]

Dive a MK25T.
Has over 200 dives in last year of which 80-90% on nitrox.
Reg started whistling so did the usual fix - more christolube on the piston and o-ring. OK for a few dives. Now whistles loudly.
Opened up to find rust mixed with the lube.
Opened a few steel tanks to check for rust - some had a light dust - others nothing. BTW the filter is sparkling clean.
My questions are ...where is the rust coming from?
is the piston rusting because it is not titanium?
is the high use of nitrox a contributing factor?
dust particles getting through the filter and getting stuck in the lube?
Is this causing the whistling?
Suggestions anyone?

 

[rescuediver009]

It is seldom one factor that contributes to the rust, but rather a combination of many factors. I don't think that it is the piston not being titanium that is causing it. It may be the high use of nitrox that titanium regs are not meant for. I would take a closer look at the entire reg. I would take it apart and take a look at all the pieces and take a look at all the pieces and see where the chrome has come off and caused the corrosion. And then just replace that part.

 

[Scubakevdm]

Take it back apart and flip the spring over. Rinse your reg in freshwater after every dive and then hang it so that water doesn't pool in the first stage. Sometimes I see light rusting on the ends of the springs.

 

[DA Aquamaster]

Whistling in a piston first stage is virtually always caused by inadequate lubrication of the HP o-ring. Flipping springs, etc is frequently cited as a cure, but it is the removal and reinsertion of the piston required to flip the spring that usually results in more lube usually getting to the the required spot that does the trick, although success is often short lived as there is again inadequate lubrication in that area if no additional lube is added. The HP o-ring and bushings are areas where I get pretty liberal in applying christolube and in doing so I regularly get 100-130 dives between services with no problem with whistling.

If you are getting rust in the lube I'd disassemble the whole reg and inspect it. If it is coming from the tank, there should be traces in the filter and there should be a light dusting in the HP section of the reg.

If the rust is forming in the ambient chamber, the rusting parts (the piston or spring) should show signs of rusting.

I have found that with the large ambient ports on the Mk 25 that spending time inside rusty wrecks can cause fine particles of rust, silt, etc to end up in the ambient chamber and some of this can stick to the christolube used to coat the piston stem and spring. In that case of course, the rust in the ambient chamber is not from the reg at all.

 

[cavesprite]

Thank you for your suggestions - the extra lube helps with the whistling.

Scubapro sure do love christo-lube!!

However, now feel pretty confident that the high use of nitrox is a major contributor to the problem of rust. Switching to a std MK25 - the titanium was a gift and although one doesn't look a gift horse in the mouth ....a first stage is another matter!

 

[wmspdi]

I have a Mk25, X650 and Atomic SS1 inflator/octo for recreational diving. I am having the same whistling problem 3 dives after an overhaul. Needless to say I am sending mine back to be re-done. The Scubapro is a good regulator for warm water but...

If you are going as far as scrapping the MK25T why not scrap the Scubapro all together and look at an Atomic M1. The M1 is a balanced and sealed 1st stage (great for cold water), you can use up to 80% Nitrox if dedicated to hyper pure air. The 2nd stage has a heat sink, adjustable cracking pressure control knob, and it has an automaic VIVA system that adjusts for depth (no having to flip the switch on and off at the surface). If you are a cave diver you can get a "cave ring" to make it easier to disassemble the second stage under water if needed. A very nice swivel hose is available as an option.

It also has a seat saving feature that backs the seat off when the regulator is not under pressure. Recomended overhaul period is 2 years and the warranty is not dependant on maintaining even that extended service schedule. They don't supply free overhaul parts (but O rings are cheap anyway), it's the yearly labor charge for the service that gets you. The fit and finish are outstanding and the designers are old Scubapro guys that went off on their own.

I bought an M1 1st/2nd stage and an M1 octo and couldn't be happier with it. I plan to use it for cold water diving in Lake Erie and for "black water" diving with our sheriff department's dive team. I'm going to hang on to the MK25 for warm water vacation diving... until I can afford an Atomic T1x Titanium for travel... then the SP is outta here.

 

[Scubakevdm]

Let me know if you want to get rid of that whistely old Mk25/x650.

 

[wmspdi]

Let me know if you want to get rid of that whistely old Mk25/x650.

I joined my sheriff department's dive team recently and I'm a little tapped out from buying some new gear. I have to hang on that whistely old MK25/X650 it until I can afford the T1x. Right now it's also doubles as my pony bottle regulator (yea, I know about DIR).

 

[DA Aquamaster]

I misread your post slightly and missed that you had a Mk 25T.

The Mk 25T is not on the approved list for use with Nitrox. It is the spendiest reg in the line and has a lot of snob appeal but it is in reality about the least capable Mk 20/25 ever made.

I would agree your problem is due to nitrox use but am not sure if the material is rust or not. The surface of titanum first stages reacts badly with high 02 concentrations and I suspect whatever it is you have is some by product of that reaction.

The newer stainless/aluminum version of the Mk 25 is nearly as light and much more capable when it comes to Nitrox. The all brass Mk 25 is much more affordable and approved for use with Nitrox mixes over 40% as well as 100% O2 at pressures up 3500 psi.

 

[WarmWaterDiver]

You may have a galvanic cell action going on with dissimilar metallurgies (titanium shell, non-titanium guts) aggravated by high O2 concentrations. I would not continue to use the titanium first stage with enriched O2 mixtures. Titanium is a VERY highly reactive metal - and this is one reason why it is so corrosion resistant in certain applications - it forms a surface film of corrosion product very quickly, and the resulting metal compound is normally quite tenacious, so it's like a protective film. But when you start fiddling with high O2 concentrations, you'll initiate or accelerate reactions that would otherwise occur a lot more slowly or not occur at all. Titanium will burn (like magnesium) under the right conditions - if all you're seeing is a metal oxidation product so far, my guess is you've been lucky.