Metals & TBN...

[SonofJoe]

I think everyone on BITOG has at some stage seen the Calcium & Magnesium numbers on a VOA.

I've been doing a bit of Google-fu & come up with a little rule of thumb to translate VOA metals into TBN which someone might find useful.

If you see 1000 ppm of Calcium in an oil, it will be roughly equivalent to putting 2.6 TBN into the oil. This will be true regardless of whether the over based Calcium detergent is based on Sulphonate, Phenate or Salicylate chemistry. This rule holds because regardless of what chemistry you employ, you will essentially have the same Calcium Carbonate (and to a lesser extent, Calcium Hydroxide) in colloidal suspension.

If you see 1000 ppm of Magnesium in an oil, it's roughly equivalent to putting 4.2 TBN into the oil. Likewise this applies to most chemistries. Please note that for the same amount of metal, you get more TBN bang for the buck from Mg.

If you take something like Amazon's Basic 5W20 which (according to PQIA) contains 1,927 ppm of Ca & 18 ppm of Mg, you can simply estimate their respective TBN contributions as 5.01 & negligible. The oil has a measured TBN of 6.68 so you know 1.67 TBN is coming from non-detergent sources such as ashless dispersant, diphenylamine AO or whatever.

Do bear in mind that bum results happen all the time so if things don't stack up, don't blame me!

 

[Shannow]

Nice...thankyou.

 

[JAG]

2.6 and 4.2 entered into memory. Thanks.

 

[RDY4WAR]

Great info! Thanks SoJ.

What about sodium?

 

[SonofJoe]

Sorry. I looked but I couldn't find a product data sheet for overbased sodium sulphonate. Sodium sulphonate is more of a cutting oil thing which isn't something I know much about. I was genuinely surprised when I read that Valvoline were using it in PCMO.

 

[RDY4WAR]

That's what I thought as well. Valvoline aren't the only ones that use it. Peak oil does as well.

Let's apply this to this VOA of Red Line 5w-30. The level of calcium is 3,462 ppm. Going by 2.6 TBN per 1000 ppm, this gives... (3462 / 1000) * 2.6 = 9.0012 TBN.

Yet the VOA says 8.57 TBN. Error?

 

[SonofJoe]

Not so much as error as test bounce. It plagues the lubes industry all over. You might think these tests should be spot on every time but they're not. Lubes is very much a 'near enough' kind of business.

 

[FlyNavyP3]

Great rule of thumb for estimating TBN of a finished lube when the data isn't published. Thanks SoJ!

 

[emod]

Great info SoJ!
This is what I found about overbased sodium sulphonate:

"A lot of overbased sulphonate have been commercialized, including calcium sulphonate with a TBN of 300—400[1-2], magnesium sulphonate with a TBN of 400[3], sodium sulphonate with a TBN of 400 and other sulphonates, and the preferred alkaline group is carbonate."
Overbased magnesium sulphonates has good anti-rust performance and low ash content compared with overbased calcium sulphonates, while the overbased sodium sulphonate markedly reduces engine piston lacquer film and has a much better detergency, but the condition for preparation of overbased sodium sulphonate is rigorous, and its storage stability is not ideal and is liable to adsorbing water during storage and usage.The borated sulphonate demonstrates better anti-oxidation and friction reduction performance, abrasion resistance, thermal stability, and hydrolyzing stability[4]
Source: Preparation and Performance of Overbased Complex Sulphonates, Hou Dianguo, (Research Institute of Petroleum Processing, Beijing 100083).

Other source:
"Overbased calcium and sodium sulfonates are used as EP additives. The total base number (TBN) for these additives ranges from 300 to 400."
Here: https://www.scribd.com/document/120607289/TLTEPadditrives907 (text above Figure 1)

Hope this help...

 

[SonofJoe]

Thanks emod. Good stuff!

Okay, based on what I've now read & a lot of supposition, I'm going to say that if you see an oil containing 1000 ppm of Sodium (from overbased Sodium detergent), that's equivalent to adding 1.8 TBN.

This is lower than the TBN factors for Calcium (2.6) and Magnesium (4.2) which makes it a relatively inefficient detergent.

Why? As I explained above, the active ingredient in all metallic detergents is the mineral, alkaline carbonate salt. In both calcium carbonate (CaCO3) & magnesium carbonate (MgCO3) there is one metal atom to every carbonate ion. In sodium carbonate (Na2CO3) there are two metal atoms to every carbonate ion. This 'dilutes' the percentage of carbonate in the molecule which makes for less TBN boost for a given amount of metal.

Thinking about it, what we all need is a super efficient overbased Beryllium detergent. It's almost certain to be toxic to humans but hey, you can't have everything!!

 

[emod]

Thank you SoJ for all of your efforts that gives us a better understanding about TBN contributions of different metals

 

[RDY4WAR]

Thank you, SoJ! I'm writing all of this down.

 

[PimTac]

It should be clarified that most manufacturers do not use sodium additives any longer due to the new SN+ d1G2 certifications.

Valvoline stopped using sodium around a year ago.

 

[fdcg27]

I've read that Mag offers better TBN retention than Calcium but is also more abrasive.
True?

 

[wemay]

Great stuff!

 

[RDY4WAR]

Originally Posted by fdcg27
I've read that Mag offers better TBN retention than Calcium but is also more abrasive.
True?


We discussed that recently here.

https://www.bobistheoilguy.com/foru...ergents-magnesium-vs-calcium#Post4881839

 

[SonofJoe]

Before this thread dies, I thought I might say something about overbased metallic detergents and their role in keeping 'combustion products' dispersed in the oil. For the sake of argument, I'll restrict this to what you get with gasoline engines.

For the most part, when you burn gasoline (a hydrocarbon) in air (N2 & O2) the products of combustion are carbon dioxide (CO2), carbon monoxide (CO) & water (H2O). These, along with any excess air, pass out through the exhaust and don't generally react with your oil.

Modern gasolines tend not to contain a great deal of sulphur but if they do, this will burn to form a range of sulphur oxides (SOx). Likewise, modern gasolines contain virtually no nitrogen but if they do, it will burn down to form a range of nitrogen oxides (NOx). You will also get some NOx from nitrogen & oxygen in the air reacting at high combustion temperatures.

Both SOx & NOx are strongly acidic in nature & will react with the weak base (eg Calcium Carbonate) at the core of your oil's overbased metallic detergent to form Calcium Sulphate, CaSO4 & Calcium Nitrate, Ca(NO3)2. Just as with the original Calcium Carbonate, these mineral salts get 'mobbed' by lots of organic detergent molecules and kept colloidally dispersed in the oil.

Although it's not directly a product of combustion, as base oils are attacked by oxygen in hot blow-by gas, they can liberate organic acids. For the sake of argument, say this is simple Acetic Acid (vinager). This will again react with overbased metallic detergent to form a salt; Calcium Acetate. This too will be 'mobbed'.

Base oils are complex chemical mixtures & it's the aromatics in base oils that are most likely to be attacked by oxygen. This will yields heavier aromatic acids eg salicylic acid. Just as before, these will react to form the Calcium Salicylate salt & will be dispersed by the detergent.

What I wanted to get across here is that what's happening here is a process of 'displacement'. Weak Carbonate salts are attacked by acids to form other salts but the amount of salt dispersion going on is, in essence the same at the start of the oil's life as it is at the end.

For other combustion nasties, eg soot & partially burnt fuel, dispersion of these is more likely to be dealt with my the ashless dispersant in the oil.

Hope this helps...

 

[SR5]

Thank you Joe, always very interesting.

 

[emod]

Originally Posted by SonofJoe
Before this thread dies...

Thread like this never dies. It just waits patiently for the seeker.

 

[SonofJoe]

I want to revise something I said earlier.

Trawling Google, I found an old 1988 Amoco patent which contained some actual data on overbased Sodium sulphonate. The neat detergent had a TBN of 409 & a Sodium content of 17.6%. On this basis, 1000 ppm of Na in oil would be equivalent to adding 2.3 TBN.

This is higher than the 1.8 factor I estimated originally. I'm guessing the difference could be due to small amounts of unreacted, residual sodium hydroxide in the detergent (NaOH is a very strong base). That said, sodium is still a more inefficient detergent than either calcium or magnesium which goes some way to explaining its relative unpopularity.

Interestingly, the patent also included some info on an overbased Potassium sulphonate detergent. This stuff had a TBN of 158 & a Potassium content of 12.5%. So 1000 ppm of K in oil would only impart 1.26 TBN. This is even worse than Sodium and reflects the basicity 'diluting' effect of having two relatively heavy metal atoms to one carbonate ion in K2CO3.