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n contrast to inland environments, devel-oping scopes of work for coating andlining storage tanks at oil and gas termi-nals on the U.S. Gulf Coast requiresattention to the challenges of frequent

rain, high heat and high humidity. The pres-ence of pervasive moisture and heat calls forthe availability of expertise when selecting theappropriate products to keep the project ontrack and within budget, and most important-ly, to provide outstanding corrosion protectionto critical plant assets.

This article will discuss the latest coatingtechnologies for protecting all parts of petro-chemical storage tanks situated in thesecoastal settings. We will examine: 1) a fastreturn to service (RTS) tank lining; 2) a newapproach for protecting a tanks floating rooffrom ponding water; 3) a high-throughputpolyaspartic urethane coating for atmospheric

exposures; and 4) spray-applied thermal insula-tion as a permanent solution to the corrosionthat occurs under standard insulation andcladding.

Internal LiningsFrom a macro viewpoint, standard-cure tank lin-ing materials are a sound choice for protectingthe internal floors and shell walls of most tanksin immersion service. These materials are easyto apply, cure to service in approximately fiveto seven days and generally perform well.However, in certain instances, putting tanksback into service the same day or overnightmakes economic sense, and coastal environ-ments can present such a scenario.

In Gulf Coast settings, dehumidificationequipment and, in winter, heating equipment,must be supplied by the contractor to maintainrequired environmental parameters during the

application process. Newer lining materialsthat cure in less than 24 hours can significant-ly reduce the costs of renting this equipmentover the course of a project, and positivelyinfluence inspection time frames as well as theoverall project schedule, while still maintaininga very high level of corrosion protection.

Fast RTS tank linings can handle a broadspectrum of cargos within the petrochemicalsegment including ambient temperature crudeoil, gasoline, jet fuel, diesel fuel, kerosene andethanol. These linings are most commonlymedium-film materials (20 to 60 mils DFT)available in amine, phenolic and novolacresins. The resins are sometimes combinedwith micaceous iron oxide and/or glassflake/ceramic beads in order to enhance cor-rosion protection.

Fast RTS tank lining materials, many ofwhich are self-priming, are applied with plural

Achieving Efficiencies with Coatings and Linings Work

in Gulf Coast Environments

IPhoto courtesy of Shutterstock, Inc.

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and condensate. The welded carbon steelroof is designed so that the roof floats on thecommodity and rises and falls based on thelevel of the liquid in the tank. Thus the vaporspace is minimized, reducing the evaporativeand volatile emissions into the atmosphere.

In the Gulf Coast region, rainwater will col-lect and pond in the low areas of the roof.When combined with the fallout from the adja-cent refinery or chemical processing facility,and exposure to UV rays, a severe corrosivecondition is activated.

In traditional external floating roof new con-struction and maintenance, a thin-film two-coat system of an immersion-grade epoxyhas been the standard in the oil and gasindustry. The coating is applied at 5 to 6 milsDFT per coat with a total of 10 to 12 mils

DFT. These systems are normally applied overmultiple days and project schedules are oftenimpacted by the fast-developing rain prevalenton the Gulf Coast.

However, nowadays owners are seekingsolutions to achieve a 20-year service life fortheir external floating roof coatings. Oneoption is to improve the coating system andthe barrier protection by increasing the DFT to20 mils with a medium-film coating system.

Adding additional DFT brings with it extraconsiderations. The performance of the coat-

ing system at an elevated temperature rangecannot be compromised in any way, and theheat of the commodity can raise the floatingroof temperature to as much as 130 to 140 F.Therefore, the coating system will requireapplication capability at this temperature.

component spray equipment, utilizing two pro-portioned pumps (standard-cure materials useonly one), heated hoppers and spray lines, anda mixing manifold setup.

Utilizing plural component equipment andapplying the lining in only one coat minimizesthe time, expense and environmental disposalcost created with the multiple equipment sol-vent flushings necessary with conventionalcure systems. While this equipment is becom-ing more common in contractor service offer-ings, it does require an onsite foreman andcrew trained in the distinctive application tech-niques involved.

A separate issue is the condition of the tankbottoms, i.e., whether the substrates are heav-ily pitted or new. It is important to note that inhot weather (above 90 F), the substantiallyshorter dry times of fast RTS materials mustbe factored in, in order to allow open time forthe product to flow into and fill all pitted areaswithout producing excessive holidays and dis-continuities.

Ultimately, the expense of heat and dehu-midification is making owners receptive to theidea of fast RTS tank lining materials. It can bea game-changer option for owners accus-tomed to standard-cure materials that mayrequire weeks to put tanks into service, and itreduces the cost of onsite inspectors who willbe able to oversee repairs and final inspec-tions within a much shorter time frame.

External Floating RoofsBecause of its attributes, the fast RTS tank lin-ing system is increasingly being employed toprolong the service life of a tanks externalfloating roof. External floating roof storagetanks are utilized at terminals and refineries tostore petroleum products such as crude oil

By Ron Knecht, Regional Market Segment Director, Oil & Gas, North America, The Sherwin-Williams Company

Pictured is the newly finished interior of a crude oil storage tank where a routine inspectionrevealed a significantly degraded floor. The owner did not have time to wait for standard linings tocure, so a fast return to service lining was specified. Photo courtesy of Sherwin-Williams.

External Cone Roof/Shell SystemThe qualifications for coating systems for atanks external shell and cone roof in a GulfCoast environment are also in a state of evo-lution. The industry standard for dealing withthe high humidity, salt spray and rain of thesesettings has been the three-coatzinc/epoxy/urethane system. However, overthe past few years new materials have beendeveloped that are extremely moisture toler-ant, provide quick dry-to-handle times andoffer superior corrosion protection.

Polyaspartic urethane resin technology pro-vides a coating with the long-term corrosionresistance and exterior durability of a conven-tional urethane finish coat with dry-to-handletimes the market hasnt previously seen.These next generation coatings are capableof application to 9 mils DFT in a single coat,and cure to be rain resistant, even in highhumidity, in as little as one hour.

For light to moderately corrosive environ-ments, these coatings are available as single-coat direct-to-metal (DTM) one-coat formula-tions. In the highly corrosive Gulf Coast envi-ronment, they may be applied in one coatover either an organic or inorganic zincprimer after abrasive blasting to provide thetotal system thickness and performance pre-viously only obtainable by installing the stan-dard premium three-coat zinc/epoxy/urethanesystem.

Elimination of one coat of the conventionalsystem potentially removes several days andsignificant labor cost from the painting sched-ule, and the fast-cure properties of the polyas-partic urethanes include early moisture resis-tance, greatly diminishing the risk of rain orfog damaging the freshly painted finish coat.

Thermal Insulation In most petrochemical facilities, tanks, pipingand valves in hot service are insulated bypreparing and priming the steel, wrappingthem with insulation materials such as mineralwool or calcium silicate, and then cladding

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In addition to ensuring the suitability ofapplying the product on a hot steel substrateintended for ponding water service, specifica-tion considerations include application condi-tions and the flexibility of the product, as wellas the need to address coating edge retentionon the weld seams to avoid premature corro-sion, ensuring the single coat will provide thesame degree of coverage as it would on theflat surfaces.

It should also be noted that because it willtake several days for the entire roof to beblast cleaned and fully primed, the substratemust be protected for the duration of the pro-ject as work is completed each day. To pre-serve the blast-cleaned substrate over thecourse of those days, a fast-drying epoxyprimer or organic zinc-rich epoxy primer isapplied at 2 to 2.5 mils DFT.

A fast-cure 100% volume solids edge reten-tive epoxy applied with plural componentspray equipment is utilized as the finish coat.Also required is a stripe coat of the finish coaton the weld seams and edges prior to apply-ing the finish coat. The fast RTS coating canbe exposed to foot traffic in as little as onehour and cure-to-service is eight to 24 hours.This condensed curing schedule versus theconventional multi-coat/multi-day system sig-nificantly diminishes the risk of weather-induced project delays. As with the interior lin-ing application, the fast dry times allow forexpediting the holiday inspection procedure.

Flexibility is also a key criterion for the float-ing roof coating system. The steel plates on afloating roof will exhibit movement and thecoating system must have enough inherentelongation properties to prevent cracking andpremature coating failure, particularly at theincreased 20 mil DFT.

After the final application, the coating sys-tem should be inspected for holidays andproperly repaired. The 100% volume solidsepoxy finish coats for touching up holidayscan be supplied in a brush grade version orare available in plural component cartridges.

Coatings Work in Gulf Coast Environments

them with light metal jackets to protect insula-tion from elements and minimize moisture intrusion.

Conventional insulation, while very efficientwhen dry, loses much of its thermal insulatingproperties once it is permeated with moisture.Frequent rains and high-humidity conditions pro-vide endless moisture which infiltrates either asliquid or water vapor under the insulationcladding, saturating the insulation material. Theresult can be catastrophic in its effects, and isknown as corrosion under insulation (CUI).

Two problems are set in motion here: first,the insulation value is greatly diminished as theair in the insulation material is replaced by waterwhich is exponentially higher in thermal conduc-tivity. Second, the moisture combines with air-borne chemicals and salt as well as the insula-tion material itself to become an ideal electrolytefor corrosion cells to form on the asset sub-strate. This corrosive activity is hidden, andoften not discovered until full rust-through of thesubstrate has occurred. To combat this safetyand reliability issue, expensive spot inspectionfor CUI is often employed.

Increasingly, owners are opting to installspray-applied, non-clad thermal insulative coat-ings that provide a monolithic barrier to water,chemicals, UV rays and heat transfer. They alsoprovide personnel burn protection, thermal insu-lation for energy conservation, condensationcontrol and protection from radiant solar heating.

Formulated from waterborne acrylic resinswith ceramic and glass beads or microspheresthat minimize energy transfer through the filmdue to its high air content, these coatingsadhere to the underlying primer and preventwater or moist air from corroding the steel. Theair content is so high in these coatings that theweight of a liquid gallon is only about 5 to 6pounds, with much of that weight evaporatingout during the drying process.

Because there is no cladding involved in thesystem, spray-applied insulative coatings can bemonitored for corrosion and maintained like any

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paintsquare.com / JPCL December 2014 35

other external coating system. Thermal insula-tive values will remain constant and pre-dictable. This means that assets insulated withthis modern system can be removed from theexpensive CUI monitoring protocol.

Thermal insulative coatings can be spray-applied on surfaces operating at up to 350 Fover primers that are either zinc-rich (organicor inorganic), high-temperature-resistant epox-ies or multipolymeric matrix silicones. All threeof these primer technologies can perform welldepending on expected temperature, the sur-face preparation that could be attained andthe application technique available. They arealso less labor intensive and safer to applythan conventional clad insulation.

To achieve the desired thermal properties,the coatings are applied in multiple fast-dry-ing coats, then finished with a chemical andmoisture-resistant acrylic topcoat for long-

term performance. Unlike conventional insu-lation, this system will repel water and mois-ture vapor and maintain its original insulat-ing properties in any weather condition. Withan unlimited recoat window, maintenancepersonnel can handle periodic repair andtouch-up, and the system can be washed toremove dirt, mildew and other surface cont-aminants.

ConclusionsWithin the oil and gas market segment, own-ers, specifiers and coating contractors canbenefit from being aware of the latest trendsin protective coatings in order to extend assetlife and achieve efficiencies in application andmaintenance. Updating coating and liningspecifications to include materials that willaccommodate typical Gulf Coast weather con-ditions can pay significant dividends, both in

short-term scheduling and over the assetslifecycle.

About the AuthorRon Knecht is Regional Market SegmentDirector, Oil & Gas, North America, for The

Sherwin-WilliamsCompany. He has heldvarious positions atSherwin-Williams since1985, specializing in protectivecoatings in the oil andgas market since 1993.

He has been a member of NACE and SSPCfor more than 20 years and is a NACE Level3 Certified Coating Inspector. He holds aBachelor of Science degree in business man-agement from Oklahoma State University. JPCL