Full transcript
0:00let's talk about zinc dialthiophosphate
0:04sometimes also known more commonly as
0:06zddp or just plain zinc and while we're
0:09going to talk about it because everyone
0:11talks about it when it comes to pcmo
0:13stuff
0:14the reason why it's such a
0:20let's talk about zinc dialthiophosphate
0:23more commonly known as zddp or sometimes
0:26just referred to as zinc and the reason
0:28we're going to talk about it is because
0:30everyone talks about it when it comes to
0:32pcmo everyone talks about zinc the
0:36amount of zinc the types of zinc why
0:38zinc is going away it's a bit of a Hot
0:40Topic now why is zinc necessary going
0:44back to the strive curve remember there
0:45are three different lubrication regimes
0:47we've got boundary we have mixed and we
0:49have hydrodynamic and you can sort of
0:51think of them as being let's say there's
0:54different areas of the curve are catered
0:57to by different parts of the formulation
0:59so with elastic hydrodynamic it's the
1:01base oil viscosity that is doing all of
1:04the heavy lifting when it comes to mixed
1:06and Boundary we're relying more on
1:09things like the anti-wear in the EP
1:10package right
1:12and so we can basically think of the
1:15left part of the curve as being
1:16dominated by the additive pack and the
1:18right part of the curve being dominated
1:19by the base oils now zinc dial
1:22thiophosphate kind of looks like this
1:25right this is a rough sketch of the
1:27molecule and the important part is
1:29actually this thiophosphoric acid so
1:32phosphoric acid on its own can be a
1:35reasonably potent anti-way additive the
1:37problem is it's an acid It's relatively
1:39corrosive and so we need to neutralize
1:41it
1:42with something like zinc oxide so if we
1:44take two thiophosphoric acid molecules
1:46and we neutralize it with the zinc oxide
1:48what we get is zinc are diarykyl
1:50thiophosphate and a little bit of water
1:52left over now how does it kind of
1:55activate what is this zinc or zddp
1:58molecule actually doing well when it
2:01gets into the load zone so let's say
2:02that this is I don't know two bearing
2:04surfaces or you know a cam and a cam
2:08lifter
2:09as it um as it gets into this area
2:12the well this is theorized by the way no
2:16one's ever actually seen it happen in
2:18real time so what's theorized is that
2:20basically the molecule breaks apart
2:21right and then the activity of the
2:24sulfur and the phosphorus kind of bonds
2:27it to the metal surface and it starts to
2:29form this sacrificial anti-wear film now
2:32if we zoom in on the anti-wear film what
2:33does it look like well it's very thin
2:36for starters it's only in the order of
2:3750 to 150 nanometers so invisible to the
2:40to the human eye and it kind of consists
2:43of these layers there's like this iron
2:45sulfide zinc sulfide layer which is
2:47followed by a polyphosphate layer and
2:50then at the top we have this sort of
2:51zinc polyphosphate now that is supposed
2:55to be sacrificial so it exists on top of
2:58the metal surface and when the two
3:00metals come into contact with each other
3:01it's instead this layer which rubs away
3:03rather than the metal itself right so
3:06that's functionally how it works
3:09all right the thing about zinc though is
3:12that it has multiple functions so when
3:15we talk about for example the auto
3:16oxidation cycle talked about this in
3:18other videos
3:20um
3:20zinc is actually very effective at
3:23dealing with peroxides so peroxides are
3:26the rooh molecule that you see right in
3:29the middle
3:30so zinc functions as what we call a
3:34peroxide decomposer right so it
3:36interacts with the rooh and sort of
3:40um helps negate the oxidation activity
3:43of that molecule
3:46this is broadly how it happens right so
3:48roughly zinc you know if you have about
3:51four of them it's able to neutralize it
3:53into a a less reactive molecule right
3:57so zinc or zddp is a fantastic
4:02technology it provides us with
4:04anti-wear capability and it provides us
4:07with antioxidant capability and it does
4:09so at a very very low price point in
4:12comparison with other molecules that are
4:14available on the market
4:16there is one major problem with zddp and
4:19that's got to do with how it interacts
4:21with catalytic converters so catalytic
4:24converters are obviously on the vast
4:27majority of cars that you'll see out
4:28there with the exception of things like
4:30race cars and what they are designed to
4:32do is take nox as well as carbon
4:34monoxide and transform it into inert
4:37nitrogen as well as carbon dioxide so
4:40take some harmful molecules and turning
4:42them into much less harmful molecules
4:43now if you peel back the layers what's
4:46inside a catalytic converter
4:49right it's this ceramic honeycomb com
4:52combined with these Rare Earth
4:54stabilizers now the problem with zinc
4:57dialthiophosphate is that when you look
4:59at this molecule it is supposed to be
5:02reactive it's supposed to react with
5:03Metals otherwise like that's exactly how
5:06it is able to bond with let's say the
5:09cams the cam lifters uh the the timing
5:12chain the gears it's supposed to bond to
5:16metal surfaces and it does so because
5:18the sulfur and the phosphorus are quite
5:21reactive in this molecule unfortunately
5:23right what that is going to do is it's
5:26also going to react with
5:28the metals in a catalytic converter So
5:32eventually you what you get is a buildup
5:33of sulfur and phosphorus and so when a
5:36carbon monoxide molecule is trying to
5:38react with the the Catalyst it can't
5:40find an active site right and so that
5:44inhibits the capacity of the catalytic
5:47converter to do its good work
5:49so what we've seen over time is
5:52especially you know among the the ilsac
5:54and the API and the Acer specifications
5:56is this slow lowering of the allowable
6:00phosphorus sulfated Ash and and sulfur
6:03limits right they slowly slowly come
6:05down
6:07you can see that in a lot more detail in
6:09in the current regulations right
6:12so as these have slowly come down
6:16that has presented a little bit of a
6:18problem
6:18because we need zinc to help preserve
6:22the Integrity of the engine
6:24so how do we get around it when we are
6:26able to use much less zinc
6:28well there's a couple of ways right
6:31first of all
6:32not all zddps are equal
6:35some that are more equal than others
6:37so when we look at a zddp molecule right
6:41there are and theoretically an infinite
6:44number of zdtps so if you look at this
6:46these are groups that I've highlighted
6:47on the sides they can be any kind of
6:51molecule that is attached to zdep and
6:54you've probably heard the terms you know
6:55primary and secondary zdps so what
6:59exactly does that mean well if you can
7:01imagine that we have a straight
7:04chain of carbons attached to one of
7:07these oxygens right
7:09that's called an alkyl zddp so we'll do
7:13this again for the bottom one
7:15right now what we have
7:18um at the top right is what is called a
7:21primary alkyl group and down the bottom
7:23this is called a secondary alkyl group
7:27and that gives you a primary zddp versus
7:30a secondary zdp now what makes it a
7:33secondary zdp is that the first carbon
7:37attached to the oxygen right has another
7:40molecule attached to it so it's not just
7:41hydrogens that's what is a a secondary
7:44zdp then if I were to have some kind of
7:48um
7:49you know different functional group this
7:51one for example is what we would call an
7:53arrow functional group and that gives
7:55you an arrow zddp so zdp belong to a
7:59actual family of molecules they're not
8:01all the same and they have different
8:02performance properties right so you've
8:04got the difference between arrow and
8:06alkyl and among the alkyl groups you've
8:08got the differences between primary and
8:10secondary zdps so arrows it has been
8:13found form anti-wear films slower
8:17and then when you look at the difference
8:19between primary and secondary zdp is
8:21primaries seem to volatilize off a
8:23little bit faster right and secondary
8:27zdps seem to be
8:29let's say the most capable of the zdps
8:34now this is still an ongoing area of
8:36research and so the mix between our all
8:39primary and secondary is something which
8:43um you know oil companies are continuing
8:45to investigate about what is the optimum
8:47combination but as we start to refine
8:50the effectiveness of different types of
8:53ddps we can actually use fewer of them
8:55and get the same effect right so that's
8:57how in some cases we're able to lower
8:59the amount of zinc but still have the
9:01same anti-ware effect
9:04this isn't the only change that we've
9:05made though we're starting to add in new
9:08molecules so as an example you've
9:10probably heard of the term Molly right
9:12well Molly in engine oils is usually
9:15comes in the form of a molecule called
9:17molybdenum difficultamate which is shown
9:20on screen here now molybdenum kind of
9:23works in a relatively similar way you
9:25can see that it has a lot of sulfur in
9:26it
9:27so it is surface active but the
9:30challenge that we have is that because
9:32there is sulfur in it right and remember
9:34sulfur is something that we don't want
9:35because of the catalytic converter
9:37there's only so much Molly that we can
9:39use
9:40however what we have found is that the
9:42zinc molecules and Molly molecules are
9:44what we call synergistic which means
9:46that you know one plus one equals three
9:50right it so happens that when you
9:52combine zdp and molybdenum
9:55difficocarbamate you get
9:57um you know it's not completely additive
10:00right the two kind of work together and
10:02make each other more effective
10:04so that is one of the other ways that we
10:07have been able to enhance the anti-wear
10:09performance of modern engine oils
10:11finally changing base oil strategy can
10:14have a reasonably large effect too and
10:16it can help us to cope with lower levels
10:18of zinc so for example it was very
10:20common back in the day that we were
10:22using group ones uh engine oil
10:24formulations now group ones you'll see a
10:27little bit of a splash of it maybe as
10:29you know effectively uh almost like an
10:31additive but now it's much more common
10:33for the engine oils to be made anywhere
10:35between a Group Two and a group four now
10:38why is this important for anti-wear well
10:41remember when we go back to our
10:44discussion about elasto hydrodynamic
10:46lubrication this is a lubrication regime
10:48which is
10:50you know very important for bearings
10:52cams as well as gears now
10:56the elastro hydrodynamic
10:59regime forms when the fluid is trying to
11:02get through these very very narrow Gap
11:04and what happens is that that fluid
11:05compresses and it forms a really stable
11:08fluid film which is able to separate the
11:10uh let's say the two surfaces right so
11:14what effectively happens is that you get
11:16an increase in viscosity with pressure
11:18right but the relationship between
11:22viscosity and pressure is not the same
11:24for all base oils right so
11:27you know a group for pao is able to
11:32sustain our higher viscosity with the
11:36same internal pressure
11:37now what does that mean practically it
11:40means that where for example if I had a
11:43group one that was my my base oil maybe
11:47the two metal surfaces are coming into
11:49contact with each other and therefore I
11:51need anti-wear additives to help protect
11:54the metal surface but if I were to
11:57switch that same oil for let's say a
11:59group three or a group four
12:01at the same operating conditions so the
12:04same speeds and the same temperatures
12:06that group 3 or group four would
12:08actually support more load and it would
12:10separate out those surfaces now I don't
12:12need as much anti-wear because the metal
12:14surfaces are not actually coming into
12:16contact with each other
12:17so
12:19yeah this was a slightly complicated
12:21discussion about zinc the merits of zinc
12:24and why there's less zinc in modern
12:25engine oils now there's a whole nother
12:27discussion to be had about you know
12:30um old engines right because there are
12:32you know hot rods and and and you know
12:35Top Fuel dragsters and all that kind of
12:37stuff which require more zinc because
12:38they're much more heavily loaded or
12:40maybe they have different cam profiles
12:42and things like that but this is a basic
12:44discussion about why zinc has been
12:47reducing in engine oils and how it is
12:50that we can do that without engines
12:51falling apart