2009

Copyright 2009 by NACE International. Requests for permission to publish this manuscript in any form, in part or in whole must be in writing to NACE International, Copyright Division, 1440 South creek Drive, Houston, Texas 777084. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. Printed in the U.S.A.

Heavy Duty Glass Flake Coatings for Arduous Anti-CorrosionSeNice.

Charles J Watkinson MICorr. MSOE. MIMI. MIRTE. MIPel.CORROCOATI GLASS FLAKE LTD

Forster Street,Leeds LS1 0 1PW

England.www.corrocoat.com www.glassflake.com

ABSTRACT

Glass flakes have been used for a number of years to reduce gas and moisture vapourdiffusion through coating and paint films. Advances in glass flake production over morerecent years, have allowed thinner and more consistent flakes to be produced. This hasled to investigative work into the properties that can be attained by way of using glassflake as a performance improver. The work has investigated many materials both organicand inorganic and in many areas of use - such as lyres and even cosmetics. But, thebiggest field of application is in organic resinous materials, not least of which, are thoseused in the area of corrosion protection for arduous service. Surprisingly, although thethin flakes (below 2 microns) are better performance improvers in most applications insome applications thick flakes (over 5 microns) are found to give better results.The high aspect ratio of a flake compared to fibres or granular fillers imparts uniqueproperties to materials to which they are added but great care has to be taken inchoosing addition level, thickness and size distribution to obtain the required result andfor the optimisation of a particular characteristic. This work is tedious, time consumingand expensive but endeavour and patience can be amply rewarded.

Areas of interest where the addition of glass flake can make significant improvementsinclude; fire retardancy, mechanical reinforcement, UV light resistance, Tg and heatdistortion, reduction in moisture vapour or gas percolation. Changes in the properties ofthixotropy and viscosity, abrasion resistance, dimensional stability. Improved propertiescan be achieved not only in thermoset and thermoplastic materials such as unsaturated

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Paper No.

09009 2009

Copyright 2009 by NACE International. Requests for permission to publish this manuscript in any form, in part or in whole must be in writing to NACE International, Copyright Division, 1440 South creek Drive, Houston, Texas 777084. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. Printed in the U.S.A.

polyester, polypropylene and PTFE but also in materials such as paper and cement.However, these properties are combined to the greatest effect in paints and coatingsused for corrosion protection and in particular heavy duty barrier coatings. Coatingsproduced using this technology have been shown to give outstanding performance andthese have been used in industry, sometimes with good and sometimes exceptionalresult.

Keywords: Coatings. Fire Retardancy. Filler. glass flake. Heat Distortion Temperature.Moisture Vapour Transmission. MVT. Reinforcement. Epoxy. Vinyl Ester. Gas DiffusionBarrier. Barrier Pigment. Corrosion Protection. Anti-Corrosion. Ultra Violet LightResistance. High Temperature Coating. Cathodic Disbondment. Atlas Test Cell. ColdWall. Undercutting. Aspect Ratio. Silane. Pipe. Flow Lines. Chemical Resistance

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INTRODUCTION

There are many fillers and pigments used in the paint and coatings industry. Some ofthese are useful as corrosion inhibitors, some as simple extenders to reduce resin cost,some to enhance mechanical properties and some simply as a colourant. Glass flakes donot add colour (except when they are themselves coloured) and rarely can they beclassed as extenders except in high cost resins where they may not only improveperformance but also reduce cost. But they do give significant performanceimprovements in nearly all instances where they are correctly used. Other materialscannot and do not do this in the same way. Glass fibre for instance, although givingimprovement for stiffness when used at the required volume, barely reduces moisturevapour transmission or fire retardancy. However when glass flake is used as a substitutefor the fibre, not only is the modulus and fire resistance substantially increased but alsosignificant reductions in moisture vapour transmission and gas diffusion are achieved.

Apart from component parts coatings, the bulk of coatings and paints used are based onorganic resins, however all organic coatings will, to some extent or another, conveymoisture vapour and accept gas diffusion. Preventing or resisting this is desirable and itis in this area that glass flakes initially found their niche.

Particles of a high aspect ratio (low thickness to surface area) for instance platelets orflakes, can overlap each other and present a barrier to the passage of moisture and gasdiffusion in a film by extending the path length through it. Particles of a granular orspherical nature do not overlap and offer very limited resistance. The high aspect ratio(barrier) fillers are therefore highly desirable for performance improvement.The benefits of using flake-like barrier pigments, such as mica and micaceous iron oxidein anti-corrosive paints and coatings to reduce moisture vapour transmission have beenknown for a many years. Other flake pigments with varying attributes such as aluminiumand zinc have also been used as combination chemical and barrier fillers with varyingdegrees of success.

Glass flake introduced into coatings around 1960 gradually gained popularity for severalreasons. Glass flakes have a large aspect ratio and unlike mica they are not stepped, aretotally impervious to moisture vapour and consistent in composition. Other barriermaterials commonly used are opaque and often strongly coloured. Micaceous iron oxidein particular makes coatings and paints difficult to tint in light shades whilst glass flake isclear. Not only that glass flake is chemical resistant and inert in most environments, hasgood mechanical properties and is generally considered a simple dust hazard or non-hazardous particularly when compared with fibres.

Early glass flake coatings were somewhat crude trowel or brush applied materialsbasically designed as a fibre glass composite layer but with the glass flake substitutingfor fibre. It was the late seventies before good spray applied glass flake coatings wereavailable and these were generally thought to be difficult to apply and expensive. Theywere produced predominantly with unsaturated resins used previously for hand lay up.Epoxy formulations containing glass flake only came later and until more recent timeswere few and far between. They are now an important sector of the barrier coatingmarket.

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From the early eighties glass flake coatings started to become more acceptable, as theperformance and benefits of long life became apparent. At the same time pricescompared with other coatings dropped, leading to greater acceptability within the marketplace. It was during this period that research was carried out into the use of glass flakeas a performance improver and the types of paint and coating using it multipliedsignificantly. Unfortunately, the effects of using different flake concentrations, flakethicknesses, differing aspect ratios and the unusual effects on viscosity and criticalpigment volume concentration were rarely understood. There was also poorunderstanding of how the glass bonded within the various resin matrixes. This is still truetoday of many of the companies utilising glass flake as a filler material. Sometimes theincorrect use of flake though the lack of knowledge leads to a worse rather than betterproduct but often it just leads to poorer than expected results. However, where properand diligent research is carried out, the glass flake in conjunction with a suitable resin,can give tremendous improvement and allow coatings to work where failure wouldotherwise occur. Today many different types of paint or coating resin carrier are usedwith glass flakes, including but not limited to Polyesters, Epoxies, Chlor-Rubbers, Alkyds,Coal Tars, Vinyl's and water based Acrylics.

BASIC PARAMETERS

It is important to understand that although the glass flake is impervious to moisturevapour and gas diffusion it does not present a continuous barrier in a resin matrix. Theresin carrier therefore plays a very important role i.e. glass flake cannot make a poorresin film into an excellent coating, although it may substantially improve it, but evenexcellent resins can benefit from addition of flake and performance considerablyimproved. In addition flake offers differing aspects of mechanical reinforcement thanthose attained by adding granules or fibre. Notably, by way of horizontal shrinkagereduction during polymerisation on a substrate, reducing coating and coating to substratestress.

The addition of flake will generally improve the moisture vapour transmission resistanceof almost any coating film or membrane and there may be other benefits with newproperties being imparted or improved. However, the level at which the glass flake shouldbe added, the particle size distribution and adhesion to the carrier is of paramountimportance.

Although glass flakes with aspect ratios as low as 10:1 will give benefit generally thehigher the aspect ratio the better the barrier presented. This premise has however to betempered to some extent, as out of alignment large aspect ratio flakes can afford a directpath through the film where the film is less in thickness than the nominal planar size(diameter) of the flake or cause stress raisers for crack propagation. In addition there aresome properties that may be adversely affected when using large flakes such asflexibility and elongation to break. Also for consideration, is the practicality of using largeplanar size flakes i.e., when a coating has to be sprayed the gun tip size is limited byseveral factors and the flake needs to be small enough to pass through the spray tip.Large flakes also tend to produce rough surface finishes. It is therefore common, thatflakes of around 500um and below are used for spray application and flakes above thissize i.e. as large as 1500um are rarely used except for hand applied materiais. Whencompounding flake into thermoplastic materials there are several considerations but it

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has generally been found impractical to incorporate flakes with a planar size greater than300um and most usage has been with flake of circa 180um or below.

Flake size and thickness are only one of the issues involved in obtaining performance.The quantity of glass flake added and particle distribution is also critical. It is obvious thatif thin flakes of glass are used there are many more flakes than if thick ones are used forthe same weight, and therefore the surface area to be wetted with the thin flakes is vastlygreater. This means that it is impossible to just simply state the requirement for anamount of flake as for instance 20% by weight. It may be possible to add 20% by weightof flake at a thickness of 5 um and not exceed the critical pigment volume concentrationto resin ratio (CPVC). If the same quantity by weight of a flake at 2 um thickness wereadded, then the surface area of this flake will be at least two and a half times that of thethicker one and there may be insufficient resin for wet out thus the CPVC level isexceeded. In any case the viscosity may be so high when changing from the thick flaketo thin flake that addition at the same weight becomes impossible.

It is obvious from the preceding statements that once a thickness of flake has beenchosen it is important to optimise the addition level. That level will depend upon the typeof resin being used and what other pigments or fillers are being used in conjunction withit. A further consideration is whether or not coupling or bonding agents are used toprovide better adhesion of the glass flake to the resin and the substrate. 'Adhesion playsa substantial role in the performance of organic materials in corrosion protection. Thebonding of fillers into the resin is also a very important facet in obtaining performanceboth from a corrosion resistance point of view and in mechanical performance. Silaneshave been used for many years in the glass fibre industry to improve bonding and inconsequence performance. This improvement in performance is seen both as anincrease in some of the mechanical properties and a decrease in moisture vapourtransmission. In thermoset resins it is possible to get substantial improvements inperformance simply by adding the silane chosen to the resin component either justbefore or just after the glass flake is added. With thermoplastic materials however this isgenerally not possible and the glass flake has to be pre-treated with silane. It isnoticeable that pre-treated flake will improve the bonding performance in thermosets to ahigher level than that achievable by adding the silane indirectly via the resin.

Where the silane is added to the resin, it is observed that there is a critical level and theoptimisation peak is often very steep. This is true for each particular resin, glassthickness, particle distribution and addition level, it should also be noted that other fillersor additives such as thixotroping agents will affect the optimisation level. Where thesilane is added by pre-treating the glass then the level of silane used is not so critical,provided that saturation of the flake, causing agglomeration, is not achieved. It is alsoobserved that with pre-treated glass a much higher level of glass flake can be added tothe resin and in particular to thermosets without exceeding the CPVC level. One down-side of using pre-treated flake however, is the cost and a possible change in safetyhazard classification.It seems fairly obvious from the foregoing that barrier pigments with high aspect ratiosand in particular glass flake cannot simply be added at a nominal value if good resultsare going to be obtained. Specifiers of coatings containing glass flake often state theminimum loading of glass flake and a thickness for the product to be applied at, but whatknowledge do they base this on?

5

Even if the characteristics of a particular resin and formulation are known, productformulation rather than performance specification can be dangerous2. For example aspecification could state 'Epoxy with a minimum glass flake loading of 20% by weight.This level of addition could in many formulations exceed the CPVC level and the coatingwould therefore give better performance at lower glass flake loadings. In addition neitherthe flake thickness nor planar size nor particle size distribution is specified. It is thereforepossible that a coating with very high performance could be precluded from being usedunder such a specification regime whilst a pooriy performing material met the criteria. It ismore sensible therefore, that performance criteria rather than formulation criteria arespecified.

With new production methods glass flake can be produced for various purposes atconsistent thickness from around 10 um to as low as 100 nanometres and almostlimitless particle size distributions are possible. The effects of thickness, particle size,volume concentration etc., were evaluated in glass flake coating formulations usingflakes of differing thickness and diameters and with differing particle distributions. Someof the results were surprising, others expected and because testing was carried out overa wide range of properties and not just diffusion and corrosion resistance, someinteresting parameters were discovered. Of particular interest was the amount of fireresistance provided when using glass flake, a reduction in smoke emissions, heatdistortion and creep, and reduction in shrinkage during polymerisation, especially in thehorizontal plane. These results led to work also being done on non coating applicationsand engineering thermoplastics.

EXPERIMENTAL

Evaluation of various coating materials, thermoset resins and composites wasundertaken.

Test Involved

Moisture Vapour Transmission (MVT).Water Absorption.3Modified Atlas Cold Wall (Osmotic Blister) TestingCathodic DisbondmentGlass Transition (Tg) (DSC) and (DMTA)Fire and Flame Spread Resistance.Abrasion Resistance.Chemical ResistanceAnd a variety of Mechanical Tests.Some of the test work conducted and the results are shown it has not been possible toshow the full set of tests or the results obtained.

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EVALUATION OF FLAKE PLANAR SIZE ON PERFORMANCE

Tests were carried out to evaluate the mechanical performance of a glass flake filledpolyester system with flake thickness nominally 2.7 um and two different nominal planarsizes, these being a 050 of 180um (1) and a 050 of 575um (2). The loading was 15% byweight in each case. See Table 1.

TABLE 1

TEST TEST RESULT 1 RESULT 2METHOD/STD 180um 575um

COMPRESSIVE BS 6319: Part 2: 632 kg/cm 2 359 kg/cm 2STRENGTH 1983 8984 psi 5051 psi

FLEXURAL BS 2782: Part 10: 164.6 171.4PROPERTIES Method 1005 : 1977 @ @

v~. (three point method) 0.85 kg (1.87 Ibs) 1.1 kg (2.43Kg Ibs)

% ELONGATION BS 6319: Part 7: 0.6% 0.05%TO BREAK 1985

ADHESIVE BS 3900: Part E1 0 132.3 kg/cm2 79.38 kg/cm 2STRENGTH 1882 psi 1120 psi

SHEAR BS 6319: Part 4: 198 kg/cm2 208 kg/cm 2STRENGTH 1984 2821 psi 2953 psi

HARDNESS ASTM 0-2583 40.0 Rockwell H 52.0 Rockwell38.2 Barber Colman H

43.2 BarberColman

IMPACT BS3900: Part E3: 9.5 J (Nm) Forward 8.2 J (Nm)STRENGTH 1973 2.0 J (Nm) Reverse Forward

(Drop Weight) 2.0 J (Nm)Reverse

ABRASION Taber H -18 435 mg loss 415 mg lossSTRENGTH 1 kg weight

1000 cycleHEAT Differential 92C 96C

DISTORTION Scanning 197.6F 204.8FTEMPERATURE Calorimetry (DSC)

LATERAL CURE COR102 8.5% 3.9%SHRINKAGE

Test data obtained at 20 Deg C on standard cure.

It is interesting to note the substantial reduction in cure shrinkage found when using thelarger flake, the significant difference in compressive strength and elongation to break.These effects caused simply by increasing the aspect ratio of the flake.

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EVALUATION OF VARYING FLAKE CONCENTRATION

Tests were carried out to evaluate the change in moisture vapour transmission affordedby varying the flake concentration. A vinyl ester resin was used as the carrier resin withthe only difference in the materials tested being the addition level of glass flake.Tests were conducted initially to zero in on the area of criticality, then levels of 14%,15%and 16% by weight were used to carry out the main evaluation.

TABLE 2TESTED IN ACCORDANCE WITH ASTM D1653

glass flake average result ofconcentration 5 samples Permby wei,ght inches 10-5

14% 10.6115% 3.4616% 3.64

As can be seen from these results the quantity versus permeation curve is very steepwith a 1% change in the addition level changing the permeation rate from 10.61 to 3.46.A further addition of glass changes the permeation rate for the worse but only marginallywith further additions (not shown here) showing a progressive worsening as the CPVClevel is approached and exceeded. Subsequent additions show a rapid increase in MVT.This steepness of the MVT performance curve is not always so high. In some instancesthe curve is a gradual slope at both ends with a flat bottom. This type ofaddition/performance curve is preferred as this allows not only some deviation forproduction tolerances but it also allows the formulator to look at other properties i.e.mechanical or fire retardancy, without compromising the other aspects. Glass at athickness of approximately 5um allows an addition of some 24% and has an optimumreduction in MVT at around this level. Whereas glass at a thickness of approximately2.2um can not be added above 20% loading without detrimental effects but has a MVTrate reduction almost a magnitude better than the 5um flake and this is achievable overthe range of approximately 14 to 18%.

CATHODIC DISBONDMENT TESTING

The test evaluates electrical resistivity, moisture content, adhesion to the substrate andalkali resistance all in conjunction.Each of the four aspects if adverse will effect the end result. The same variations in glassloadings were evaluated for Cathodic Disbondment in the same resin matrix as thoseabove and the results are shown below.

TABLE 3CD TESTED TO BS3900 F11

glass flake concentration average of 3 testsby weight disbandment14% 5.0mm15% 3.4 mm16% 4.9mm

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The results show a similar pattern to that of the moisture vapour transmission testsexcept that in this instance the 16% result is nearly as bad as the one at the 14% level.

EVALUATION OF BONDING AGENT lEVEL

In order to evaluate the addition levels of the organo-functional silane bonding agent andits criticality, a standard vinyl ester glass flake formulation was used with the level varied.Tests were then carried out to evaluate the performance of each cured sample.

As can be seen from the table overleaf, the addition level of 0.6% Silane improves theperformance of the coating considerably. It is interesting to note that although the bondstrength is slightly better on the 0.95 level in all other respects the properties are verysimilar to those of the 0.2 addition level. Some of the test work showed initially worseresults with silane addition over no addition until the level was further increased.

TABLE 4ADHESION EVALUATION VINYlESTER COBAlT/DEAlMEKP CURE. (glass flake 15%)

level A B C D E0.2% 0.4% 0.6%S 0.8% 0.95%

Silane Silane i1ane Silan Silanee

WaterPermeability 1.86 x 10" 0.41 x 0.34 x 1.06 x 1.63 x 10"4(perm/inch) 10.4 10" 1D

0.120 0.0345 0.100 0.147 (24Water 0.148 (24 (24 hrs) (24hrs) (24hrs hrs)

Absorption hrs)(%wt.gain) 0.312 0.198 0.317 0.350

0.358 (7day) (7day) (7day) (7day) (7day)

0.512 0.447 0.435 0.444 0.486 (14(14day) (14day) (14day) (14day day)

)

AdhesiveStrength(kgfm2) 500 587 625 585 557

7 DayBarcol 49 50.2 51 49.7

Hardness 49

BendTest -Angle

coating 11 16 20 14 10Cracked

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EFFECT OF PARTICLE SIZE DISTRIBUTION ON BLISTER RESISTANCE

Further test work was carried out to evaluate any change in performance by altering theparticle size distribution. The test work was carried out by using micronised glass flakewith a thickness of approximately 2.2um and a nominai planar size of 80um and a 050 of50um in a resin formulation and comparing it with a formulation which contained thesame quantity of flake but which had a different particle spread e.g. 050 of 35um.Evaluation of performance was carried out by using a modified Atlas cold wail ceil withdemineralised water and a temperature gradient across the film of approximately 60 OegCentigrade.

The test results showed that the formulation with the smailer glass flake (050 =35um)had worse performance than the existing coating (050 = 50um). This was shown by theextent of osmotic blistering. Formulations were then produced with the glass beingblended. A significant performance improvement was achieved when the glass wasblended at a ratio of approximately 60/40 (being 60% of the 050 = 50um, 40% 050 =35um) with the test panel showing no osmotic blistering occurring at ail where previouslyboth panels had shown blistering.

EVALUATION OF THIXOTROPIC PROPERTIES

Tests were made to evaluate the differences in viscosity and thixotropic properties of astandard coating formulation using glass flake. Work was carried out using glass flake ata thickness of circa 5um and 1.3um. It had been apparent from previous test work thatthe thinner the glass flake the more surface reactive it appears to be, to the extent thatflake of a thickness below 1um can be bonded together dry simply by using a lightpressure. This reactivity seems to come from hydroxyl groups on the glass surface.When the glass flake is first manufactured there is no moisture on the surface. This isobviously a good point at which to apply the silane-bonding agent if any is to be used(although some silanes require moisture for bonding).As the glass ages over a few days moisture is adsorbed onto the surface and there is aslight weight gain coupled with a drop in reactivity. This moisture can only be driven offby using temperatures in excess of 360 Oeg C but on cooling moisture wiil reattach overa period of a few days if left exposed to atmosphere. The moisture uptake wiil vary withsurface area and the number of hydroxyl groups on the surface so this weight gain canbe used to give some measure of surface reactivity. From evaluations the thinner glassflake has always shown substantiaily greater reactivity than the thicker glass flakeindependent of surface area.Although not considered as a thixotroping agent it was thought that there may be somesynergistic effect capable of being used to benefit thixotroping. For instance in reducingthe amount of fumed silica within a coating film.

A standard formulation containing 5um flake was used as a reference material, theviscosity, thixotropic index and hold up on a vertical surface being measured. Variousformulations were then produced with 1.3um thick glass flakes. The Brookfield viscosityand thixotropic index were measured and a reduction in the fumed silica thixotropingagent made to compensate. The formulation which produced the nearest viscosity andspray characteristics was then used for further evaluation. The viscosity's, thixotropicindex and hold-up thicknesses are shown below.

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Table 5HOLDUP COMPARISON

Viscosity Th ixotropic Hold Up um.5/50 rpm index

5um glass 21,000/84 2.5 550umflake 001.3um glass 34,000/97 3.54 700umflake 00

The glass flake level in the second formulation was reduced by 4% over that of the onecontaining 5um glass but is estimated to have a surface area more than twice that of theoriginal formulation. The thixotroping agent, fumed silica was also reduced by 50% forthe second formulation, demonstrating the thixotroping properties of the thin flake andgiving a value to it.

PROCESSING/MIXING TIME

One of the areas which greatly affects the performance of the glass flake within thecarrier is the mixing time used after all flake is in the resin. Mixing time affects both wetout, distribution and ultimately break-down of the flake, having significant impact upon notonly MVT rate but also the mechanical properties of the resultant coating. Tests werecarried out to evaluate the parameters using an unsaturated polyester resin and differentgrades of flake, compounding of the glass flake into the resin was done using a Z-blademixer. The test results showed that mixing times for optimum product performance varysignificantly dependant upon flake thickness, particle size and addition level (amount).The smaller planar size flakes required a longer mixing time than the other flakes withlarger aspect ratios.

Microscopy shows that the samples contained poorly dispersed flakes after 45 minutesmixing but even distribution of the flakes after 60 minutes, and subsequent micrographstaken of specimens that had been mixed for 75 and 90 minutes show breakdown of theflakes occurring.

Overall, the higher the flakes' apparent volume content in the specimen, the better themechanical properties that specimen provides, given that satisfactory mixing is achieved.

Once the parameters in the preceding are understood, what can b achieved even withrelatively small additions of glass flake can be quite startling. It was shown in a test inPrague University in 1990 that a service tolerant coating that had 3% glass flake addedto it substantially improved in substance over the solely granular filled material. Thisenabled the product to be used in areas where previously it would not satisfy the dutyrequirements and considerably extended the market potential.

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TABLE 8

The Research Institute for Protectionof Materials, University Of Prague.

o 10 20 30 110 50 60 70 80 90 100Time (Hoursj

Glass Flake FilledSompleRC3

Granular FilledSomp'e RC4

resled occOid ng 10 BS27B2Port 5: Me hod 513AFilm rhickness: 175 mcrons

~

"C'I.0- 10.----------------,:>-0>98 8'Bi 7E 6 5~ 4:>8. 3g 2@ 1~ 0 -\L~=;==;:==;:~==;:::=:;::::;:::::;::::~g

The preceding work and evaluations show that there are and substantial benefits gainedfrom using glass flake barrier pigmentation and several properties that can be achievedthat cannot be obtained with other fillers. There is however a need to ensure that theformulation is specifically tailored for optimum performance. It is no use simplyadding arbitrary amounts of arbitrary thickness and arbitrary particle size glass flake andof course the type and amount of bonding agent will vary not only with resin type but thesurface area of the glass flake within the formulation.

There are some negative aspects in using glass flakes, these relate primarily to reverseimpact resistance, stiffness and cost although not all materials are affected in this way.The cost of flake glass in some applications can some times prove prohibitive but inmost cases the improved performance more than justifies the additional cost andwhen whole life cycle costing is taken into account they can nearly always be thelowest cost.

Looking at coatings to give performance in oilfield service and particularly in productionareas care has to be taken to get high performance and this is a never ending researchand development task. 4There are fewer coatings that perform well at high temperature, so morecare is required in selecting coatings for use in environments that will see temperatures above60C. It is even more difficult to select coatings that will see immersion service above95C.

OPTIMISING THE TECHNOLOGY

Corrocoat has over the last 15 year been researching the use of various resins to obtainhigher temperature, corrosion resistance performance, in combination with chemicalresistance and ease of application in the field. The latter being of paramountimportance for all but a few applications. There are some exotic materials that performwell at temperature but need extensive heat post cure, not practical in the field, andsometimes laboratory type application conditions, these were excluded.

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It was thought that by taking a technologically advanced resin system, that in it's ownright gives excellent chemical and temperature performance, then enhancing thatperformance utilising the foregoing glass flake knowledge to get it even better, that,would allow us to give corrosion protection in many areas covered only by expensive andsometimes ineffective metallurgy at present. Vinyl esters have been used to excellenteffect for many years and have slowly improved in performance. But non the less, thisresin is generally restricted in aqueous immersion to circa 90C and something better wasrequired.

With the above parameters in mind research was carried out into epoxies of varioustypes and using various cures, high temperature vinyl esters, sol-gels, organic/inorganicmixtures and hybrid or polymer alloy resins. This research has been carried out over anumber of years and materials were not evaluated simultaneously. Although some resinsystems were obviously not suitable from the outset general test parameters were set.

The resins were tested on their own (no fillers or thixotrope) for Tg and MVT rates atwhat were thought to be suitable thicknesses for the material concerned. They were thentested in immersion using Atlas Cold Wall test cells at ambient pressure andtemperatures of circa 90C with tap water. Where a resin looked promising i.e., it did nothave extensive cracking, delamination or blistering it was formulated into a coating usingthixotrope and glass flake. The levels of glass flake etc, the coupling agent, curing agentetc., were varied to evaluate performance improvements or deterioration. Thesematerials were then tested in pressurised Modified Atlas Test Cells at temperaturesgradually increasing from 110C upwards but mainly at 150C (the aqueous immersionlimit of the existing 'in use' formulation) and then 180C.Some of the evaluation work is listed below:

Phenolic Epoxy Novolac/BF3 Cure

BF3 Activator used in conjunction with a Phenolic Epoxy Novalac Resin was tried. It washoped that this system would form ether linkages which would give rise to a moretemperature resistant coating. This system requires a 75QC post cure which wasconsidered practical in the field. However, when immersed in water at 150QC this materialcracked significantly and de-laminated after one week.

The BF3 accelerator was then blended with another epoxy resin in an attempt to createenough exotherm heat in the epoxy/amine reaction to initiate the epoxy/BF3 reaction.This did not improve the performance of the system. Several trials on this theme resultedin no useable materials.

Silanol Functional Resin

A high temperature resistant silanol resin was filled with calcined alumina, glass flakeand a range of different pigments (Ti02 , red iron oxide, black iron oxide, green chromiumoxide) in attempts to polymerise the resin at ambient temperature.

However, these materials could not be made to cure at room temperature and it wasdecided to evaluate with cures at high temperature. Following a cure at 130C the various

13

coatings were immersed in water at 150QC. The best coating was in an unacceptablecondition after only one week.

Phenolic Epoxy Vovalac/Siianol Functional Resin System

A Phenolic epoxy Novalac/Siianol resin blend was made. This resin blend was filled withglass flake and calcined alumina. When subjected to immersion in water at 150QC thecoating was found to fail in some areas after one week but large areas of the plate werefound to be in an acceptable condition. Fumed silica was incorporated into theformulation to create a more stable and homogenous base. This formulation was postcured for 8 hours at 80QC and subjected to immersion in water at 150QC for four weeks.This coating withstood these conditions and was in an acceptable condition afterwardsbut was showing signs of impending failure. In an attempt to further improve the extent ofcure of the silanol component within this system had cobalt octoate incorporated into it.The resulting coatings performed worse than the formulations containing no cobaltoctoate.Different resin blends were incorporated into the system as it was claimed by the resinmanufacturer that a blend of two different types would give rise to a better cured fiim. Theresuiting coating was extremely brittle. It cracked and delaminated under immersion inwater at 150QC after just one week.

Initiai adhesion results for the best formulation were very low averaging around 600psibut removai of calcined alumina from the formulation increased the adhesion value from600psi to 1200psi. A temperature/cure study was conducted by coating Atlas Cell platesand curing these coatings individually at 80QC, 70QC, 60QC, 50QC and ambienttemperature (approx. 20QC). Coatings cured at ambient temperature performed as well as80QC post cured samples when immersed in water at 150QC. However all faiied afterseveral weeks immersion. It was decided to try and optimize the film thickness and testagain. The initiai formulated material was applied at a range of WFTs from 300IJm2000IJm and immersed in water at 150QC.

Silane Trials EPN/DC 805/A2410B75 Resin System

A range of silanes were incorporated at 0.01 %, 0.05%, 0.1 %, 0.5%, 1.0% and 1.5% intothe formuiation in an attempt to improve adhesion of the resins to the filler particulatesand substrate. These were:

3-glycidoxypropyltrimethoxysiianephenyltriethoxysilaneaminopropyl triethoxysilaneTrimethoxyvinylsiianeTetraethyl orthosilicatePolydimethylsiloxane

For the formulation containing 3-glycidoxypropyltrimethoxysilane the adhesion valueincreased from 1200psi to 1550psi.Formulations containing silane performed worse thanformulations with no silane when immersed in water at both 150C and 180QC. With allformulations containing silane the base gelled within 2 weeks of storage at ambienttemperature. Amino functional silanes were incorporated into the activator to avoid the

14

storage issues but these formulations performed poorly when immersed in water at150QC.

Sol Gel

This system consisted of silica hydrogel (SiOd dissolved in potassium silicate solution,treated with methyltrimethoxysilane and zinc dust as the second component of a twopack system. Dilatancy issues were experienced in the manufacture of the base. Extrawater was used to overcome this problem. Some zinc dust within this formulation wasreplaced with glass flake. The resulting coatings performed poorly when immersed inwater at 150QC and Intercoat adhesion was poor. They also performed poorly whensubjected to salt spray tests. It was hoped that the addition of zinc dust would besufficient to catalyse the reaction but this appeared not to be the case as formulationscontaining zinc or zinc and glass flake did not perform better than the formulationscontaining only glass flake.

GLASS FLAKE GRADE CHANGES

It was decided to look at the effect on the grade of glass flake added to some of theformulations previously evaluated to see what the effects were on this system comparedwith previous knowledge at lower temperature evaluation. The micronised flake within theformulation was replaced by milled flake in an attempt to improve the mechanical andbarrier properties. Atlas Cell plates were coated using this formulation change andimmersed in water at 150QC. One coating survived for six weeks before failure due tocracking in the non-immersed area only. A noticeable improvement on the previousformulation which survived immersion in water at 150QC for one week.

In order to get a greater glass to resin ratio a much larger glass flake thickness wasincorporated into a formulation at a higher percentage in place of the previous flake toreduce the resin content and observe any improvements in cold wall performance. Afterone month surface cracking was observed in the non-immersed area. After two monthsslight surface cracking could be observed in the immersed area and the cracking in thenon-immersed area had become slightly worse but the coating continued to protect thesubstrate from corrosion. After three months the coating had deteriorated slightly more inthe immersed area and the non-immersed area but continued to protect the substrate.After four months the coating deteriorated further and appeared to have stoppedproviding corrosion protection in the non-immersed area. Surface cracking could beobserved in the immersed area and it was unclear if this coating was protecting thesubstrate at this stage.

Formulations using the large glass flake at high percentages were found to survive underimmersion in water at 180QC for three to four months - a significant improvement over theprevious formulations and totally contradictory to extensive previous work that had beenconducted.

Using this information the existing in service Vinyl ester/Urethane Hybrid wasreformulated with thicker glass (7um) and at a higher loading. Significant performanceimprovements were observed at the higher temperatures (180C).In an attempt to further improve the properties of the coatings evaluated. Formulationswere prepared using blends of different glass thicknesses and particle size, as previously

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this had shown significant improvement, as mentioned before. Three different filler blendswere used but unexpectedly, all three filler formulations at several loadings, performedmuch worse than the formulations containing only the single size large glass flake.

Porosity/Bubble Reduction Study

A lot of work was carried out on removing surface skips and micro voids in the coatingsbut no performance improvements were made using the various surfactants and bubblerelease agents tested. After various trials this work was abandoned.

GENERAL

Although there were several materials that, theoretically, looked promising, and somesurvived the initial pressurised Atlas Cell test regime - only one consistently performed atthe minimum temperature requirement of 150C immersion, the existing 'in use since1996' coating. This is a Vinyl ester/Polyurethane Hybrid.

Using some of the information gleaned over the years of trials, the glass size and contentwas changed in this coating. That gave some performance improvements at 180Callowing a better margin in continuous service in aqueous media at 150C and in nonaqueous media as high as 180C. In gas environments the coating has been used andstood the test of time to temperatures as high as 280C.

4This material also tested well in an evaluation carried out in Canada for the "While it isnot a definitive method of comparing the coatings, it is interesting to note that there wereonly two (2) of the thirty-one (31) coatings that had good performance in at least six (6) ofthe eight (8) tests"

Service: The hybrid glass flake coating has been used in various corrosive environmentsincluding; High temperature heat exchanger shells, water and condensate environment atbetween 100 and 160C., Sodium Base exchangers, Salt water environment between 90and 120C., Aluminium Chlorohydrate Reactor where aluminium is dissolved into HCLand process agitated with steam., Waste gas absorption tower, circa 150C., Flare Stackpre heaters at 180C, Nickel Sulphide quench tank operating between 100 and 140C.,demineralised water pre heat tank at 120C., and Crude oil flow lines operating up to160C., High temperature waste incineration: Waste gas scrubber operating at 200C withexcursions to 400C. There are many more examples but the most relevant to the TarSands expansion is the examples from the Duri Oil Field in Indonesia.

In the Duri field, the Bitumous Oil is extracted using a mixture of steam and solvent. Theground conditions over and through which the production lines run is considerablyvariable in pH but can be very acidic and the water table can vary from above groundlevel to some metres below in the same location dependant upon season and rainfall.This results not surprisingly in the external corrosion rates of the pipe being severalmagnitudes that of the internal rate. The pipes were generally either coated with abitumen based coating but many other coatings had been tried or left un-coated whichseemed reasonable considering the expense of coating and the short life-span. Aparticular problem was at Road Crossings where the pipe through necessity was almost

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always buried and through wall leaks were reported to have occurred in as little as twoand a half months. In consequence the road crossings were not surfaced with tarmaceven on paved roads due to the constant necessity to dig out the pipework.

In 2001 coating trials began in earnest at the Duri field. Trials on the external coating ofhigh temp oil flow lines (highest temp found 176 deg C- 348 deg F) with the Vinylester/Polyurethane Hybrid glass flake for buried service in 2001 resulted in a trial contractin 2002. After this there was a pause for 2 years whilst the field customer tested a lot ofother coatings, all of which failed in a short time period. We have since learned that inanother of the customers fields that had normal flow line operating temperatures of only70 90 deg C, a dedicated facility had been built, to apply a powder coating for the buriedpipe. By the time the facility had been built, the field trial areas coated had already failedand the plant stands empty to this day. Other coatings were tried including two majorpaint manufacturer's glass flake coatings, appiied to a number of pipes and over a rangeof service temperatures. All failed within less than a year.

Following the tests our company was called back in middle of 2004 and has been coatingpipe on a continuous basis since then. We have coated the high temperature 4" flow lineswith Corrothane XT, the Hybrid Coating and the larger diameter, lower temperature pipewith Polyglass VEF, a glass flake vinyl ester coating.

At the end of 2007, 40% of the fields road crossings had been coated. In 2001 the Durifield had approximately 1200 oil leaks. An early pipe replacement program succeeded ingetting the leaks down to 250 in 2004 but at a significant capital and down time cost.However, since the introduction of the Hybrid glass flake coated pipes, we are informedthat the oil leaks have been reduced to less than 20 in 2007, with none of the leakscoming from pipe coated with the glass flake hybrid. One hundred and forty thousandlinear feet of 4" road crossing pipe has been coated and 10,000 feet of 6"-36" pipe.Production has increased significantly due to the major reduction in down time andmiddle of the night call outs are almost a thing of the past. As an unexpected bonus,most of the engineers involved with leakage program were no longer required but due tothe program's success they have all moved onto bigger and better jobs within thecustomers organization.

Other fields are now taking advantage of the specialist coatings, application knowledgeand service provided by our company. Also work expands into other areas such as theinternal coating of waste brine pipes and the corrosion protection of gate and checkvalves at three central gathering stations.

Further, due to our tremendous success in giving corrosion protection in areas previouslythought almost impossible, local operations of major American oil service companies,have taken advantage of our presence to coat frac acid tankers, waste treatment tanksand other ancillary oilfield equipment.

There are many glass flake coatings in the market these days but few of them have theresearch and background of those produced by us. Glass flake coatings properlyformulated not only give outstanding performance but also long life cycles. Whole lifecosts can be very low indeed. Many of the advantages in using glass flake, such as fireretardancy and mechanical properties have been ignored and there is still a lot of work to

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be done before all the benefits of glass flake pigments and the coatings produced fromthem are understood. They are however, very useful in the oil industry and much moreuseful than you might think!

CONCLUSION

Ongoing research and development into heavy duty ant-corrosive glass flake coatingscontinues to yield improvements. This work is time consuming and expensive but theknowledge and improvements gleaned, allow coatings to work in some of the moredifficult environments at higher temperatures. This reduces down time, maintenancecosts and in some instances negates the need for expensive metallurgy, which in its ownright, is not always successful. In several industrial sectors including oil production andprocessing there are already proven areas of application and several other areas thatcould benefit from this advanced technology.

REFERENCES

1 C.H.Hare. Protective Coatings. Fundamentals of Chemistry and Coating.

2 C.watkinson. Conference on Materials Corrosion Engineering. Petaling Jaya Hilton,Malaysia 1996.

3 J.Jelinek., C. J. Watkinson. Cold Wall Effect Testing of Internal Pipeline Coating forInsitu Application. NACE Conference1997.

4 Tank Lining Joint Industry Project. Comparative Study. Charter Coating Service (2000) Ltd.,Canada.

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