Methanolic Corrosion of Aluminum

Inquiry

I understand that there was some issue with CableCURE^®/XL fluid when deployed in Germany in aluminum stranded cables. How do Novinium’s Ultrinium 732 or 733 fluids interact with aluminum stranded cables?

Response

It is true that about 1% of cables treated in Germany in 2002 with CableCURE/XL fluid failed because of the methanolic corrosion of aluminum. Even though the incidence of failures was quite low, the failure mode was dramatic as illustrated nearby. See the image labeled “German Cable Failure” taken from Bertini, “Failures in Silicone-treated German Cables Due to an unusual Aluminum-Methanol Reaction,” (ICC October 29, 2002). In the illustration the grey material between the strands is aluminum methoxylate, the profuse formation of which caused the insulation to bulge. The bulge is described as similar to when a snake eats a rat. An analgous phenomenon occurs in low voltage cables in the presence of water. In both cases, the bulging occurs because the aluminum hydroxide or aluminum methoxylate has a very low density, or put another way, takes up a great deal of volume. Because rejuvenation is utilized to improve the reliability of power distribution cables, even a 1% induced failure rate is unacceptable.

Novinium was founded in 2003, so we enjoyed the benefit of hindsight into the methanolic corrosion of aluminum and hence we addressed this issue in all of our Ultrinium and Perficio technologies. Novinium has not had a single incident of methanolic aluminum corrosion.

To demonstrate why Novinium technology avoids methanolic corrosion, it is useful to understand the mechanism of methanolic corrosion. One compound and one element are required for methanolic corrosion to occur … the compound is methanol; the element is aluminum.

Compound

CableCURE/XL fluid, Perficio 011 fluid, and Ultrinium 732 fluid all include methoxy silanes, which react with encountered water and produce methanol as a by-product. Ultrinium 733 fluid and CableCURE/DMDB do not produce methanol as by-products, instead these fluids produce larger, less chemically reactive higher boiling point alcohols, namely 2-ethylhexanol and n-butanol.

The reaction of methanol with native aluminum (methoxylation) proceeds at a rate proportional to the concentration of the methanol. The concentration of methanol in the strands of a treated cable is influenced by four factors:

1. The amount of water that is present in the strands and the strand-shield. Less water means less methanol; more water yields more methanol.

2. The stoichiometry of the silane water reaction. Stoichiometry is chemist-speak for the ratios at which materials react. For the CableCURE/XL fluid and Perficio 011 fluids, which utilize the same monomeric silane, the maximum possible methanol concentration is about 25% by weight. For Ultrinium 732 fluid the maximum is about 20% by weight. All other things being equal, Ultrinium would enjoy about a 20% lower methoxylation rate because of the superior stoichiometry.

3. The rate at which methanol diffuses from the strand area out of the cable. The diffusion of methanol is quite fast, so the risk of methoxylation decreases rapidly for all technologies. Higher temperature accelerates the diffusion and dissipation of methanol.

4. The use of non-methanol-based alkoxysilanes reduces methanol concentration beyond the 20% stoichiometric advantage described in factor 2 above. In a patented process (U.S. patent 7,611,748 and its foreign equivalents) Novinium adjusts the formulation with more and more non-methanol-based Ultrinium 733 fluid as the anticipated temperature of the treated cable rises.

Element

Except for copper stranded cables that are immune to methanolic corrosion, at first blush it appears obvious that elemental aluminum is available in an aluminum stranded cable, but it is not. As soon as aluminum strands are drawn and laid into a strand bundle on the factory floor, the outside layer of aluminum reacts with oxygen to form aluminum oxide (Al₂O₃). Aluminum oxide forms a dense barrier that protects the underlying native aluminum metal. This aluminum oxide layer is called a patina and it protects the underlying aluminum from further corrosion.

Patina

If you take a piece of aluminum and scrape off the patina with a knife, you will see bright and shiny native aluminum underneath. In the presence of oxygen, the patina begins to reform immediately. The shiny surface will soon return to its dull grey appearance. Of course, in a power cable there are no knives scraping off the protective patina, so how did the CableCURE/XL fluid penetrate the patina? One problem with CableCURE/XL fluid and CableCURE/DMDB is the use of a condensation catalyst called titanium (IV) isopropoxide.  Also known as tetraisopropyltitanate, we will call it TIP. Over the course of Novinium’s research we learned that TIP facilitates the degradation of the patina. Novinium does not use TIP in its Perficio or Ultrinium formulations. Novinium uses a patented catalyst (U.S. Patent 7,700,871 and its foreign equivalents) that does not suffer the same problem.

A second way that the patina can be damaged is bubble nucleation or boiling. Bubbles form in microscopic cracks in the patina and their rapid expansion and sudden disappearance mechanically perturb the patina. In the discussion above we learned that Ultrinium 732 fluids enjoy about 20% less stoichiometric methanol and hence the boiling point of the mixture is higher. Put another way, it takes a greater temperature escalation for Ultrinium to produce bubble nucleation than for CableCURE/XL and Perficio fluids. The patented silanes (U.S. Patents 7,658,808 and 8,101,034 and their foreign equivalents) included in Ultrinium fluids by Novinium and our partners enjoy improved stoichiometry, mitigating methanolic corrosion. CableCURE/XL fluid is particularly egregious in this dimension, because it includes an ingredient called trimethylmethoxysilane (TMMS) that has a boiling point even lower than methanol. To mitigate the aggressive bubble nucleation of 2002 vintage CableCURE/XL fluid UTILX Corporation reduced the concentration of TMMS in CableCURE/XL by a factor of between 3 and 6. This problem with TMMS is well documented by U.S. Patent Application 2009/0114882 and its international equivalent WO 2006/119196. Besides attacking the patina the TMMS creates a fire and explosion hazard. Novinium does not use TMMS in Ultrinium or Perficio fluids.

In addition to mitigating the causes of patina damage, Novinium utilizes a patina stabilizer from BASF^®, called Tinuvin^® 123 hindered amine light stabilizer. In experiments undertaken at Novinium, Tinuvin 123 outperformed all other patina stabilizers by at least a factor of two. Tinuvin 123 has other beneficial performance attributes to extend cable life and is included in Ultrinium and Perficio fluids and its use is protected by U.S. Patents 7,658,808 and 8,101,034 and their foreign equivalents.  In a patented process (U.S. patent 7,611,748 and its foreign equivalents) Novinium increases the supply of Tinuvin 123 by increasing Ultrinium 212 fluid as the anticipated temperature of the treated cable rises.

Summary 

Novinium substantially reduces the methanol concentration using proprietary silanes, does not use low boiling and highly flammable TMMS demonstrated to cause bubble nucleation even at moderate temperatures, eliminates a patina attacking catalyst utilized in the offending formulations, and adds a patina stabilizing compound to all but prevent methanolic corrosion of aluminum in its Ultrinium formulations. Perficio technology includes the improved catalyst and patina stabilization, and does not use low boiling TMMS. Perficio suffers from a higher methanol concentration than Ultrinium technology. Perficio technology should not be utilized in high temperature aluminum-conductor applications.

To UV or not to UV

In my December 29, 2010 post at …

Crazy-Competitor-Claims

Wonderer in the Wilderness inquired …

1. How can Novinium get the same cable life extension without a soak period?  It would seem to me that Novinium puts less fluid into the cable than one would get with a soak period.

In my first post addressing this question I provided an abbreviated answer. We learned from the abbreviated answer that that when Novinium founders conceived of the first generation of treatment fluid over two decades ago we failed to check the relative diffusion rates of the phenylmethyldimethoxysilane (PMDMS) monomer and the condensation catalyst we had chosen to provide long life.  This turned out to be a grave mistake, which we have corrected.  In a subsequent post on January 3, 2011 at …

Catalytic Considerations – Component I

… I provided a more comprehensive answer, but I promised five new posts that would explain the functional improvement of the five kinds of ingredients in Ultrinium™ 732 and Ultrinium™ 733 fluids.

In this second of five sub-posts, we will explore the role of the ultra-violet absorbers (UVAs) and hindered amine (pronounced a-mean) light stabilizers or HALS.  The primary UVA is BASF^®’s Tinuvin^® 1130.  Additionally ferrocene (pronounced fair-O-seen), which was discussed in my last post, Voltage Stabilizer, is not only a voltage stabilizer, but also absorbs ultraviolet photons in the appropriate wave length.  In the vernacular, ferrocene is a “two-fer” or a “two-for-one” ingredient, because it fulfills two independent and important life-extension functions.

As you know, frog skin is very sensitive, and so I slather on the UVA (sunscreen) every time I am out in the sun – doing so helps keep me beautiful.  Cables buried one meter underground do not need protection from the sun’s relentless ultraviolet onslaught.  They do need UV protection, however, from UV that is created when space charges recombine near the ends of water trees.  Consider for example the work of Bamji, Bulinski, Chen and Densley in the Proceeding of the 3^rd International Conference on Properties and Applications of Dielectric Materials, held in Tokyo in July 1991:

“… at points of electric stress enhancement in the polymer, the light emitted during the initiation phase of electrical treeing is … due to the recombination of electrons and holes injected into the material.  The spectra of the emitted light is in the visible and ultraviolet ranges.  The ultraviolet light can photodegrade the polymer and lead to electrical treeing.”

It is easy for us all to understand how UVA materials work.  They are opaque to UV light.  The potentially damaging UV photon strikes a resonance stabilized structure in the UVA molecule, is safely absorbed, and is converted to harmless heat.  That’s how sunscreens for our skin work too.  On my skin, if I want to stop 100% of the UV photons I need to apply unattractive zinc-oxide in a thick pasty layer – yuck!  In insulation if I want to stop 100% of the UV photons, I need to apply clay – we call those insulations EPR, EPDM, et al.  So UVA materials cannot intercept 100% of the damaging UV photons.

Unlike the common experience we all have with UVA materials, HALS are not within our normal experience.  HALS are free radical scavengers and they are beneficial, because the mechanism of photodegradation involves the creation of a free radical by errant UV photons – a photon strikes an electron and imparts so much energy to the electron that the molecule, to which it was bound, can no longer hold on to it.  A free radical (an unpaired electron in the molecule) and a free electron are created.  Electrons don’t like to be unpaired, and so, they search out other electrons and try to borrow them from their parent molecules.  As they do this, they tear apart innocent molecules and generally there is still an unpaired electron after the damage from the first encounter.  The free radical survives (or spawns a daughter) and creates cascading systemic damage.  HALS quench free radicals, and here is the cool part, they auto-regenerate to a HALS after they kill the free radical.  How cool is that?  I wish they would make HALS for amphibians, because I could take a HALS pill and snack on crickets all day without worrying about the consequences of free radicals ravaging my DNA.

It gets even better.  The word “synergy” is overused in business circles and promised synergies are often quixotic.  The poster tadpole for synergy is the interaction between UVA and HALS components.  Alone, each has a positive effect on cable life, but together they work better than the sum of their parts – one plus one equals three!  Ultrinium™ 732 and 733 fluids and Perficio™ 011 fluid utilize BASF^®’s state-of-the-art Tinuvin^® 123 HALS.  As we learned in the previous post, DMDB Doubts, Tinuvin 123 also stabilizes aluminum strand patina, which all but eliminates the potential for strand corrosion suffered by older injection technology.  Tinuvin 123 provides another formulation two-fer.

For over two decades, UVA and HALS have been included in TRXLPE (tree retardant cross-linked polyethylene) formulations.  See for example U.S. Patent 4,870,121, "Electrical Tree Suppression in High-voltage Polymeric Insulation,” September 26, 1989.  With the introduction of Ultrinium™ 732 and 733 fluids, Novinium delivers improved UV stabilization using the best available technology.  Novinium’s UV package is protected by U.S. Patent 7,658,808 and other pending patents and their foreign equivalents.  Only Novinium rehabilitation technology provides UV stabilization in the proper UV range.  To learn how first generation technology fails to address the UV photons created by space charge recombination, see Section 8 of the CIGRÉ Canada paper of October 18, 2010, “Cable Rejuvenation Mechanisms: An Update.”

To UV or not to UV, that is the question.  Answer:  Come out of the sunlight into the shade; live longer and with greater reliability,

Thermonuclear

DMDB Doubts

In my December 29, 2010 post at …

Crazy-Competitor-Claims

Wonderer in the Wilderness inquired …

Question 5. A new fluid, DMDB, has been introduced.  Will this improve injection performance on my URD cables?

In that first post I provided an abbreviated answer.  We learned from the abbreviated answer that DMDB is not appropriate for URD cables in particular, because of two inherent inefficiencies.  One inefficiency is by design; the other … well it’s not by design.  I illustrate the first problem nearby.  We call this property of the fluid, “stoichiometric efficiency.”  (Pronounced stoyk-E-O-meh-tric)

Stoichiometry defines the quantitative relationships that exist between the reactants and products in chemical reactions.  When any of the six monomers in the figure nearby react with water they form desirable products and some undesirable by-products.  The percentage of desirable products compared to the total is the stoichiometric efficiency.  The stoichiometric efficiency can be calculated knowing only the chemical composition.  In the graph titled “Hydrolyzate Concentration in Condensate,” this math has been performed for all alkoxysilanes of commercial significance as a function of the number of alkoxy carbon atoms, from one to twelve.  The six globally significant alkoxysilanes are each illustrated on the figure and their positions within the hydrolyzate concentration continuum are pinpointed.  The table nearby defines the acronyms and provides commentary on each monomer.

Methanol, a one-carbon alcohol, is an undesirable by-product of the first three fluids, which are generally deployed in small diameter URD cables.  At very high operating temperatures (i.e. conductor temperatures above 55°C), methanol can corrode aluminum.  Fortunately, the methanol generally diffuses out of the system very quickly and small diameter cables do not routinely experience 55°C conductor temperature.  As a consequence the risk of methanolic corrosion is quite low in applications where these fluids are properly deployed.  All Novinium fluid formulations include Tinuvin^® 123, which stabilizes the patina on aluminum strands and further reduces the risk of methanolic corrosion.  Patina (pronounced pa-TEE-na), is the natural corrosion resistant coating that forms on metals such as aluminum.

To address methanolic corrosion in larger conductor cables CableCURE^®/DMBD fluid was introduced.  DMDB’s undesirable by-product is butanol, a four-carbon alcohol.  The good news is that butanol is unlikely to cause aluminum to corrode; the bad news is that it comes at the price of stoichiometric efficiency.  In the figure nearby, I have circled in blue the portions of the silane monomers, which yield undesirable by-products.  For the DMDBS monomer, about two-thirds of the molecule provides no benefit to the cable.  Because of its low stoichiometric efficiency, you won’t find this frog suggesting that it be used for small diameter cables – especially when there are much better solutions in wide commercial application.

How about larger conductor cables?  Does DMDB do the trick with those?

In the 1980’s the guys at Du Pont discovered that alcohols with 6 to 24 carbon atoms are “tree growth inhibitor[s] capable of imparting at least a thousand-fold increase in electrical endurance as measured by an accelerated test procedure.” (See U.S. Patent 4,206,260.)  In the figure nearby my green laser is pointing to a lightly-green-shaded region of the graph that falls within the Du Pont discovery.  Instead of undesirable by-products, these longer-carbon-chain alcohols are superb dielectric enhancement fluids.  In other words, with Novinium’s Ultrinium™ 733 fluids there are no undesirable by-products, and hence the stoichiometric efficiency is 100%.  Like the 4-carbon alcohol by-product of DMDBS, the 8-carbon alcohol will not corrode the aluminum.  High performance – no compromises!

Finally, to get the total efficiency, it is necessary to consider other efficiencies including catalytic efficiency.  In my January 3, 2011 post, Catalytic Considerations – Component I, I shed some frog wisdom on that subject.  There is also a technical paper in the Novinium library titled Considerations for Injecting Cable with High Conductor Temperature, which provides even more detail.  The bottom line is DMDBS is definitely not appropriate for small conductor URD cables.  For large conductor cables the best choice is Ultrinium™ 733 fluid which enjoys 100% stoichiometric efficiency and a much higher catalytic efficiency.

Always state-of-the-art,

Thermonuclear Bull Frog

Crazy Competitor Claims

Dear Thermonuclear Bull Frog,

I recently attended a webinar on cable rejuvenation presented by another firm and need to ask some questions:

1.    How can Novinium get the same cable life extension without a soak period?  It would seem to me that Novinium puts less fluid into the cable than one would get with a soak period.

2.    The ’840/’841 patents prevent anyone from using a fluid that diffuses into the insulation quickly.  Do Novinium fluids infringe on those patents?  Won’t a fluid with faster diffusion and reactive fluids lead to faster and better treatment of the cable?

3.    Isn’t it better to have a 100% reactive fluid?  I understand that not all of the Novinium fluid components are water reactive.  When all the fluid components are reacting with water, it seems like you should get better cable rejuvenation.

4.    I see that Novinium uses an acid catalyst in their fluids.  Won’t this acid damage the cable, be dangerous to handle, or cause environmental problems?

5.    A new fluid, DMDB, has been introduced.  Will this improve injection performance on my URD cables?

Wonderer in the Wilderness

Dear Wonderer-

Wow, five questions in one inquiry!  That’s a record for this frog.  I like prolific questioners Mr. Wonderer, but some in my audience have short attention spans, so here is what I am going to do.  In this post, I will clarify some of your questions and provide abbreviated answers.  In the next few weeks I will expand on each of the answers.  When I do that, I will come back here and edit this post to include a link to the comprehensive answer.

First let me say that the technology utilized by the folks on the other end of the webinar was largely invented by Novinium founders.  If you want to use that technology, we will take it as a compliment that even our two-decade old ideas still have frog legs.

1.    You wrote:  How can Novinium get the same cable life extension without a soak period?  It would seem to me that Novinium puts less fluid into the cable than one would get with a soak period.

a.    Abbreviated answer:  When Novinium founders invented the technology that utilizes a soak period, we had never measured the relative diffusion rates of the catalyst and the monomer.  When we made that measurement a few years ago, we were a little embarrassed to learn that the previously chosen catalyst diffuses about six-times slower than the monomer.  This mismatch means that for a typical 15kV cable with a 1/0 AWG conductor, more than one-third of the fluid supplied to the cable prematurely diffuses out without undergoing the required condensation reaction.  We call this unfortunate condition, catalytic inefficiency.  As soon as the Novinium science team recognized this problem, we fixed it.  It turns out that in a typical 60-day soak period about one third more fluid is supplied, which just about makes up for the catalytic inefficiency.  Novinium patented our solution (U.S. Patent 7, 700,871).  Now, if you are enamored with soak periods and don’t mind the safety compromises and economic consequences that they entail, we can do soak periods too.

b.    Comprehensive answer:  See Catalytic Considerations - Component I and Catalytic Considerations - Component II

2.    You wrote:  The ’840/’841 patents prevent anyone from using a fluid that diffuses into the insulation quickly.  Do your fluids infringe on those patents?  Won’t a fluid with faster diffusion and reactive fluids lead to faster and better treatment of the cable?

a.    Abbreviated answer:  Ouch!  Suggesting to a circuit owner that a competitor is engaging in patent infringement is not a tactic we would use.  The short answers to both parts of this question are:  No and no.  The second half of the questions about size (i.e. faster diffusion) and water reactivity are addressed by question 3 below.

b.    Comprehensive answer:  See Size Does Matter.

3.    You wrote:  Isn’t it better to have a 100% reactive fluid?  I understand that not all of the Novinium fluid components are water reactive.  When all the fluid components are reacting with water, it seems like you should get better cable rejuvenation.

a.    Abbreviated answer:  No!

                                       i.    I know who suggested this to you, so let’s check out what he wrote to learn if 100% water reactivity really is important:  “The presence of the water reactive functionality phenylmethyldimethoxysilane within the insulation was confirmed by microscopic infrared spectroscopy (SiOMe band at 1190 cm^-1) through 54 days.  It should be noted that 1/0 AWG size cable has a small conductor interstitial volume compared to the volume of polymer surrounding.  Larger diameter conductor cables would be expected to have considerably more water reactive functionality present for dielectric enhancement over a longer period.”  [Don Kleyer & Wayne Chatterton, The Importance of Diffusion and Water Scavenging in Dielectric Enhancement of Aged Medium Voltage Underground Cables, Proceedings of the IEEE/PES Conference April 1994.]

                                      ii.    Allow me to translate.  The water reactive functionality is gone in about two months, but it would last somewhat longer in bigger cable, but shorter still in say, a No.2 AWG cable.

                                    iii.    For decades-long life extension, it is quite a stretch to suggest that water reactivity over a couple of months is critical.  But, if you want to believe what the author says now, rather than what his experiments previously indicated, we will make a special 100% water reactive fluid for you.  You see, Novinium has a patent (U.S. Patent 7,611,748) on a process of tailoring the fluid formulation to your unique conditions.  We will make a special brew just for you.  We can name it Ultrinium™/WC.  You might think that “WC” are the initials of the water reactivity proponent, but it stands for Water-reactive Confusion.

b.    Comprehensive answer:  See Size Does Matter.

4.    You wrote:  I see that Novinium uses an acid catalyst in their fluids.  Won’t this acid damage the cable, be dangerous to handle, or cause environmental problems?

a.    Abbreviated answer:  I notice that you use an acid in your salad dressing – vinegar.  I notice that you squeeze acid on your fish – lemon juice!  I think the webinar presenter is jealous of our U.S. Patent 7,700,871. We use less than 0.3%, less than 3 parts per thousand of a very large acid molecule called DDBSA.  The acid part of the large DDBSA molecule is 1 part in 332.  In other words the concentration of the acid proton is about 1 part in 111,000!  That’s like putting a teaspoon of vinegar in your bath water.  So no, there is no issue.  The same cannot be said of titanium(IV) isopropoxide (TIP), which is the catalyst used in the two-decade-old technology at a level of 2 parts per 1000.  TIP catalyzes the methanolic corrosion of aluminum.  TIP doesn’t taste good on salad or on fish either.

b.    Comprehensive answer:  The dilute acid will not damage the cable.  It has been deployed in millions of cable feet.  The dilute acid is not dangerous to humans or amphibians.  The acid catalyst enjoys profound benefits.  See Catalytic Considerations - Component I and Catalytic Considerations - Component II to learn more.

5.    You wrote:  A new fluid, DMDB, has been introduced.  Will this improve injection performance on my URD cables?

a.    Abbreviated answer:  No way!  Did the guy actually suggest that?  The active portion of DMDB is diluted by the presence of two 4-carbon alkoxy groups that serve no purpose other than to mitigate the aforementioned methanolic corrosion issue.  Fully two-thirds of the fluid is lost even before suffering the catalytic inefficiency of 60%!  Without a multi-year soak period, one could not hope to get enough DMBD into a URD-size cable to provide multi-decade life.  Rather than diluting the product to solve the corrosion problem, the other guys should switch to an acid catalyst.  Oops, they can’t, because we invented and patented that.  (U.S. Patent 7,700,871)

b.    Comprehensive answer:  See DMDB Doubts

Come out of the wilderness into the light.  The truth is well documented.  I don’t mind setting the record straight – that is what I do for a living.  I am not above having a little fun myself though, so I would like to ask a favor of you.  Wonderer, I would like to plant a question for you to ask the next time you participate in a wilderness webinar:  "Why was Novinium the only firm to participate in NEETRAC’s side-by-side rejuvenation test?"  All rejuvenation vendors were invited.  Instead of casting stones in webinars they could have put their technology directly against the technology leaders.  Here is the answer relayed by NEETRAC in a project conference call:  "[The invited supplier] chose not to participate citing 'business and commercial reasons.'”  Satisfied?

Concluding Crazy Competor Claims,

Thermonuclear

P.S.  I decided to create a whole new category within my blog to address Crazy Competitor Claims.  It will be like a rejuvenation myth busters!  I will print all civil responses from other rejuvenation suppliers, if they want to engage in a public debate on the merits of the various technology choices.  The other guys are big fans of mine; they visit this blog all the time.  I suspect they will cite “business and commercial reasons” for not engaging in a transparent dialog.

Fan the Strands

Dear Greatest Amphibian,

I have a question regarding a statement I heard one of your colleagues make at an ICC meeting recently.  Would you comment on the criticality that wire brushing of the conductor has when installing a connector?

Kindest regards,

JA at Xcel-lent

Dear JA-

You are indeed Xcel-lent because you are not afraid to ask the tough questions.  And I am Xub-erent, because I love to dispel myths.  When connectors are qualified to ANSI C119.4 do you think the manufacturers use old corroded conductors?  If you answered yes, stop reading here.  If you answered no, read on. More...