Question for the brains... :)

[fuel tanker man]

Would the depletion of ZDDP in a UOA indicate that metal to metal contact had been occurring--or at least could have occurred?

If I understand correctly, the zinc and phosphorous "sacrifice" theirselves to prevent metal from touching metal. Is that correct? When metal tries to hit metal these anti-wear elements step up, take the bullet, and get crushed into non-existence or something such?

But if the hydrodynamic film never breaks down, the zinc/phos/moly or whatever just kicks back and enjoys the ride; the EP add pack remains largely intact. Right or wrong?

So if you're looking at a UOA and you see some metal numbers which are higher than average... and you also see that the ZDDP count is down from what it was on a reliable VOA--is it reasonable to assume that those metal numbers were racked up during this OCI?

It has been advanced that high metal in a UOA may be from metal laiden old sludge which has been "washed clean" by the new oil. And that's certainly plausible.

But if the wear metals really are from old sludge, then the EP add pack should be mostly all present and accounted for.

Right?

Dan

 

[fuel tanker man]

don't tell me you guys are afraid to take this one on...

 

[Curious Kid]

Tank,

Unless I'm mistanke, Terry has the credentials (but I /we understand).

You give some good points.

It seems logical that such compounds would be depleted when playing their part sacrificially. But unless they are plated, I think that even if some decomposition cames of them, they might still present themselves in the oils analysis. If that were that case, then what may seem as a depletion or even an increase could be well accounted for by the error presented by the analysis equipment/human error.

Element/wear metal entrapment within sludge is another interesting point. Further presnting a loss/gain potential. I wonder what a used autorx treated oil analysis might show.

Because I'm only speaking in theory reather than based upon hard facts, I inevitablly come to the sense that there may be to many variables (test error %'age, plating or decomposition, decomposition products still being read by their make-up or not, sludge greneration w/element entrapment, sludge and accompanying entraped elements released, etc.).

I come back to the sense that UOA excells in trend analysis, where trouble spots can point themselves out beyond spetroscope error. Of course visc. readings, particulate counts and so forth may be higher in accuracy, but I think you get the point.

Come-on people, step right up and give it go.

 

[benjamming]

quote:

---

Originally posted by Curious Kid:
I wonder what a used autorx treated oil analysis might show.

---

Well, the 1st clean phase on my 3.1L V6 is here

My 1st rinse phase on the same vehicle is here

 

[Curious Kid]

Thanks Ben.

I had a thought this morning that even if element's had formed into a compound, a spectrum analysis would still show bands that represented the characteristic wavelength positions for each element (correct me if I'm wrong). I'm not sure how this is quantified though.

To go further in an attempt to find an answer, I feel I would need to understand how the testing equipment/process works.

The imagination at work - at least this time I don't think it's getting me in trouble!

 

[fuel tanker man]

Well guys... with all afforded respect.

Since the heavy-hitters have chosen not to wade in here, I'm going to have to tentatively conclude that a ZDDP level which is down more than about 25% from VOA would indicate that there had probably been a consistent breach of the hydrodynamic film--normal oil change intervals assumed, of course. And if wear metals are commensurately high, that would cause me to conclude (remembering, of course, I'm a layman, and willing to learn from those more knowledgeable on the matter) that the engine was "scraping," metal to metal--or at least had attempted to.

It seems that Redline's typical high metals in UOA's must be attributed either to its presumed excellent solvency, or to its (perhaps)

inability to maintain a good hydrodynamic film. The condition of the anti-wear pack here would seem to be key to understanding which of these explanations is correct.

I'll poke around the VOA's versus UOA's and see if there's any data to expand on...

Dan

 

[1sttruck]

Wear can be very localized so additive depletion can't always be assumed to be a necessary indicator of wear.

 

[MolaKule]

FTM, you hvae a number of questions mixed into the discussion. ZDDP is an organo-metallic, multifunctional additive in that acts as an anti-wear agent and as an anti-oxidant. MoDTC and Antimony DTC are similar compounds.

It is composed of an alcohol and zinc salts with phosphorus and sulfur reacted to form a tri-element compound. The sulfur atoms is the "thio" portion of the chemical description and helps to react or attract the phosphorus and zinc to the metal surface to form ferrous phosphides and zinc sulfide films.

The action of ZDDP or like compounds is to form a layer or film that becomes a plastic when the pressure of loads heats up the localized surface. Generally, there are two or more types of comounds present, one which acts at lower temps, and one which reacts at higher temps. Do a search on ZDDP or activation temps since this has been explained elsewhere.

If the UOA shows a reduced zinc presence, then one has to assume that the zinc has been taken out of the ZDDP molecule and deposited to the metal surface.

Since the ZDDP or like compounds also act as anti-oxidants, a depletion of same would indicate that the compound is reacting to fight oxidation.

And of course, as the oil volatizes, a third mechanism of depletion would be the vapors being carried to the intake system for subsequent combustion.

 

[salesrep]

Kule

quote:

---

It is composed of an alcohol and zinc salts with phosphorus and sulfur reacted to form a tri-element compound. The sulfur atoms is the "thio" portion of the chemical description and helps to react or attract the phosphorus and zinc to the metal surface to form ferrous phosphides and zinc sulfide films.

---

Are there different grade qualities of tri-element compounds?

 

[fuel tanker man]

Molakule,

Thanks for taking your time to help me understand this. I think I've been using "ZDDP" and Zinc/Phosphorous interchangeably, and after reading your answers above I now understand there's more to ZDDP than just Zinc and Phosphorous.

If I understand you correctly, the Zinc can be depleted by either acting as an anti-oxidant (as part of the ZDDP molecule) or by being "used up" as a barrier shield (as the ZDDP molecule deposits its zinc atoms onto the metal surfaces).

Is it wrong to conclude that if the Zinc is being depleted in the anti-oxidant role, that Phosphorous levels will fall commensurately? In other words, does the Phosphorous "go away" along with the Zinc when the ZDDP molecule acts as an anti-oxidant?

And if Zinc is low, but Phosphorous is not, would high wear metals tend to suggest the zinc was used up as a barrier additive, rather than as an anti-oxidant?

Thanks for your time.

Dan

 

[MolaKule]

quote:

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Are there different grade qualities of tri-element compounds?

---

Not so much different grades as different types that can be designed to react at different temperatures. The different types use different starting alchols.

Also, there are different versions with varying Zinc to Phosphorus ratios.

 

[MolaKule]

quote:

---

Is it wrong to conclude that if the Zinc is being depleted in the anti-oxidant role, that Phosphorous levels will fall commensurately? In other words, does the Phosphorous "go away" along with the Zinc when the ZDDP molecule acts as an anti-oxidant?

---

What we generally see is the phosphorus fall to a certain level and stabilize, while the zinc is is uptaken to metal.

quote:

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And if Zinc is low, but Phosphorous is not, would high wear metals tend to suggest the zinc was used up as a barrier additive, rather than as an anti-oxidant?

---

Since it is playing a dual role, it is difficult to determine if reduced levels are being used in the anti-oxidant role or the metal-protection role, or both.

 

[Shannow]

molakule,
as these reactions take place, where do the additives end up ?

As precipitates that are filtered out ?
Deposits/sludge.

'cause if the reaction products remained oil soluble, or even suspended solids, then they should still remain in the UOA.

 

[1sttruck]

(hum to 'where have all the flowers gone' :^)

Where have all the metals gone?
Long time passing
Where have all the metals gone?
Long time ago
Where have all the metals gone?
Boys have looked for them every one
When will they ever learn?
When will they ever learn?

The metals seem to end up suspended in the oil, collected in a filter as larger particles, sludge or possibly AutoRx precipitate, remain in the engine as larger trapped partcles, deposited in sludge or varnish, and get incorporated in some of the anti-wear films.

 

[salesrep]

What is the diff between hydrolytically stabel zinc compound and hydrolytically unstable zinc compound?

 

[M3 Mitch]

Now, somebody correct me if I'm wrong, but I think a regular (non-roller) cam is normally in "boundary" lubrication, ie some metal-to-metal contact happens. This is why some sort of extreme pressure additive package is necessary in any "modern" motor oil.

So depletion of the extreme pressure additives does not mean that the base oil is not doing it's job, if this is true.