Painting & Coating Industry (PCI) logo Powder coating summit logo
  • Sign In
  • Create Account
  • Sign Out
  • My Account
  • NEWS
  • PRODUCTS
  • MATERIALS
  • TECHNOLOGIES
  • FINISHING
  • RESOURCES
  • EVENTS
  • DIRECTORIES
  • EMAGAZINE
  • CONTACT
cart
facebook twitter linkedin youtube
  • NEWS
  • Latest News
  • Market Trends & Reports
  • Price Alerts
  • Subscribe to eNewsletters
  • Global Top 10/ PCI 25
  • Weekly Featured Article
  • COATLE Word Game
  • PRODUCTS
  • Product News
  • Must See Products and Services
  • MATERIALS
  • Additives
  • Resins/Polymers
  • Pigments
  • Equipment
  • Distributors
  • TECHNOLOGIES
  • Adhesives
  • Architectural Coatings
  • Industrial Coatings
  • Nanotechnology
  • Powder Coatings
  • Solventborne
  • Special Purpose Coatings
  • Sustainability
  • UV Coatings
  • Waterborne
  • Waterborne
  • FINISHING
  • Finishing News
  • Finishing Technologies
  • Finishing Equipment
  • RESOURCES
  • Columns
  • Blogs
  • Coatings Supplier Handbook
  • Podcasts and Videos
  • PCI Store
  • eBooks
  • Sponsor Insights
  • White Papers
  • COATLE Word Game
  • Columns
  • Ask Joe Powder
  • Did you know?
  • Distribution Dive
  • Focus on Canada
  • Formulating With Mike
  • Innovation Insights
  • Moody's Coatings Conundrums
  • Powder Coating Perspectives
  • Target the Market
  • TiO2 Insider
  • Blogs
  • Editor's Viewpoint
  • Industry Insights
  • Podcasts and Videos
  • COAT-IT! Podcast
  • Videos/PCI TV
  • EVENTS
  • Coatings Trends & Technologies Summit
  • Paint and Coatings Academy
  • Webinars
  • Calendar of Events
  • Lifetime Achievement Award
  • DIRECTORIES
  • Buyer's Guide
  • Equipment Directory
  • Materials Directory
  • EMAGAZINE
  • Current Issue
  • eMagazine Archive
  • China Issue Archive
  • Editorial Advisory Board
  • CONTACT
  • Contact Us
  • Advertise
  • Subscribe to eMagazine
  • Subscribe to eNewsletters
Painting & Coating Industry (PCI) logo Powder coating summit logo
search
cart
facebook twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
Painting & Coating Industry (PCI) logo Powder coating summit logo
  • NEWS
    • Latest News
    • Market Trends & Reports
    • Price Alerts
    • Subscribe to eNewsletters
    • Global Top 10/ PCI 25
    • Weekly Featured Article
    • COATLE Word Game
  • PRODUCTS
    • Product News
    • Must See Products and Services
  • MATERIALS
    • Additives
    • Resins/Polymers
    • Pigments
    • Equipment
    • Distributors
  • TECHNOLOGIES
    • Adhesives
    • Architectural Coatings
    • Industrial Coatings
    • Nanotechnology
    • Powder Coatings
    • Solventborne
    • Special Purpose Coatings
    • Sustainability
    • UV Coatings
    • Waterborne
    • FINISHING
      • Finishing News
      • Finishing Technologies
      • Finishing Equipment
    • RESOURCES
      • Columns
        • Ask Joe Powder
        • Did you know?
        • Distribution Dive
        • Focus on Canada
        • Formulating With Mike
        • Innovation Insights
        • Moody's Coatings Conundrums
        • Powder Coating Perspectives
        • Target the Market
        • TiO2 Insider
      • Blogs
        • Editor's Viewpoint
        • Industry Insights
      • Coatings Supplier Handbook
      • Podcasts and Videos
        • COAT-IT! Podcast
        • Videos/PCI TV
      • PCI Store
      • eBooks
      • Sponsor Insights
      • White Papers
      • COATLE Word Game
    • EVENTS
      • Coatings Trends & Technologies Summit
      • Paint and Coatings Academy
      • Webinars
      • Calendar of Events
      • Lifetime Achievement Award
    • DIRECTORIES
      • Buyer's Guide
      • Equipment Directory
      • Materials Directory
    • EMAGAZINE
      • Current Issue
      • eMagazine Archive
      • China Issue Archive
      • Editorial Advisory Board
    • CONTACT
      • Contact Us
      • Advertise
      • Subscribe to eMagazine
      • Subscribe to eNewsletters

    The Role of High-Performance Inorganic Pigments in Surface Coatings

    February 28, 2002


    Figure 1: Photocatalytic Cycle
    High-performance coatings are produced primarily for the automotive, industrial and coil coatings markets. Exterior durability is of primary importance; therefore the combination of color and performance is key when determining pigment selection.

    In today's world of ever-increasing expectations, the surface coater is facing a tough challenge. The ability to "think smart" has to be of primary importance in the race to differentiate oneself from the multiplicity of other suppliers, while seeking to maximize profitability.

    The pigment component in any formulation can either enhance or degrade the overall performance of the protective colored coating. In highly alkaline cement-based and silicate coatings, the chemical resistance of the pigment is crucial. In camouflage applications and substrates that cannot tolerate heat build-up, such as PVC extrusions, vinyl sidings and some coil coatings, the functionality of the pigment is the determining factor. Infrared reflective pigments, such as CI Pigment Black 30, are the pigment of choice when dark, colored coatings are required that minimize the heat retained in the protective coating. Increasingly, specifiers are looking for pigment suppliers that can correlate the relationship between pigment functionality and performance, such that the end result is enhanced durability to the finished coating.

    This article discusses the role of pigments in optimizing the durability of high-performance coatings, focusing on coil coatings as they represent a growth area of the high-specification end of the market. The benefits of inorganic pigments are discussed, deriving a direct correlation between UV opacity, accelerated weathering and lifetime. In the blue color space, pigments have been tailored to optimize color, tinctorial strength, visual/ultraviolet opacity and weatherfastness, therefore providing a cost-effective, high-performance coloring solution to coatings.

    The principal of placing functionality beyond color has to be fundamental to pigment design in order to impart assurance to the surface coater that ever-increasing market requirements can be achieved, or even surpassed.

    Figure 2: Photoactivity of Titania

    Demanding Applications

    Applications that demand high durability coatings include exterior masonry paints, coil coatings, marine paints and "super-durable" powder coatings. Exterior coatings are subjected to high temperatures in the presence of UV radiation, humidity and oxygen for long periods of time. These factors combine to initiate binder degradation, even with the most stable resin systems. Inadequate protection often promotes visible aging, with loss of gloss, poor color retention, embrittlement of the coating, chalking and delamination.

    Figure 3: Pastel Shades: Pigment and Titania

    Demanding Processes

    The inherent thermal and chemical stability of mixed metal oxide inorganic pigments offers a unique coloring solution to formulators, where high processing temperatures are involved. Ease of dispersibility, combined with stability to flocculation and gelation, are favorable characteristics influencing inorganic pigment selection.

    Figure 4a

    Demanding Binder Systems

    Inorganic pigments are compatible with pH-dependent systems, such as acid-catalyzed coatings, highly alkaline silicate masonry paints and cement slurries, and engineering polymers that can be highly reactive (polyamides and some co-polymers).

    Figure 4b

    Binder Degradation

    Most polymeric binders are inherently unstable and will degrade when aged in the presence of moisture, oxygen, and ultraviolet (UV) radiation. UV acts as the initiator to the photocatalytic cycle, as shown in Figure 1.

    Correct pigment selection is key to either enhancing or de-stabilizing the binder. In the case of a white paint, the photoactivity of titania can actually accelerate the degradation process; the photoactivity of anatase is considerably higher than that of rutile (see Figure 2).

    Figure 5
    A photon of energy is absorbed, above 3.05eV (415nm) in the case of rutile or above 3.20eV (385nm) in the case of anatase, producing an electron-hole pair. An electron is lifted into the conductivity band, leaving a gap in the valence band. Usually, the electron will drop back into the valence band, recombining with the hole. However, in some cases, proton hole migration to the surface of the titania particle initiates the following reactions.

  • Oxidation of an absorbed hydroxyl group to a hydroxide radical

  • Reduction of a Ti4+ to a Ti3+ cation

  • Reduction of adsorbed oxygen to oxygen radical

  • Free radical reaction with water to form perhydroxyl and hydroxide radicals

  • Radical diffusion into the surrounding organic medium.

    Figure 6: Effect of Pigment Protection of PVDF Substrate UV Transmission Curves in Thin Film PVDF

    Effect of Pigment Selection on Binder Stability

    When considering pigmentation of an inherently unstable system, where an unstable binder has been pigmented with titania, the role of the pigment must be for both coloration and function. For example, when formulating a colored coating, the pigment should act as a UV absorber or reflector, hence preventing UV transmission through to the binder, where degradation can occur (see Figure 3).

    Figure 7: UV Transmission of Blue Pigmented PVDF Coil Coating Films

    Factors Affecting Pigment Selection

    Generally speaking, high performance is associated with either inorganic pigments that offer relatively weak color strength, but with excellent opacity and durability; or with high cost organic pigments that offer excellent color strength with poor opacity. Formulators have a difficult choice to make between color and tinctorial strength, long-term performance and coloring cost. In all cases, pigment selection is application-specific.

    Coil coatings is an area of coating technology that is rapidly growing in importance because it provides a cost-effective method of imparting color to a cheap, metal substrate, with a low-emission coating process. Coil coaters are usually required to provide 25-year lifetime guarantees, making durability a real issue. Chalking, color fading, and loss of gloss, embrittlement, and delamination are all visible signs of degradation. This is significant cause for concern particularly within the construction industry, where replacement of cladding, roofing or window profiles is at substantial cost.

    Coil coatings are formulated from a range of polyester, polyurethane, plastisol and polyvinylidene fluoride resins. Of these, PVC plastisol coatings are the most unstable, requiring stabilizer additions. The most durable coil coating formulations are produced from polyvinylidene fluoride (PVDF), offering exceptional weathering stability. Polyester coatings dominate the scene, accounting for 60% of the European market and the majority of the U.S. market.

    Figure 8: UV Transmission of Blue-Green Pigmented PVDF Coil Coating Films
    Polyester and PVDF resins are good examples when considering pigment selection. Polyester resins can undergo photocatalytic degradation, and significant effort has concentrated on the development of UV-stabilized polyesters. PVDF, however, is extremely resistant to UV-induced radical attack, although it exhibits poor adhesion and is therefore applied onto an epoxy primer, which is highly susceptible to UV attack. The functionality of the pigment in each case is crucial - it must absorb UV in order to protect the binder system.

    The relative stability of each coil coating type is shown in Figure 4, which illustrates the following relative binder stability: PVDF > Silicone Polyester > PVC Plastisol.

    Figure 9

    Coloring Options

    If considering, for example, the blue color space, is it better to select an inorganic or an organic pigment? In this area, organic copper phthalocyanine blue is high color strength and low cost and therefore would be seen to be an attractive coloring option. Other factors must be considered, including process issues, performance and stability (see Figure 5).

    To be able to assess the protective effect that the pigment imparts to the binder, a thin film UV transmission test has been developed in-house, in a high-specification PVDF coil coating system, that has been used as a predictive tool to quantify the long-term durability of the pigmented system. Figure 6 shows that the unpigmented binder transmits UV light readily, but the pigmented films are protected and therefore exhibit superior durability. A closer look at the pigmented films shows that both ultramarine and phthalocyanine blue transmit UV in the near UV region; however, cobalt blue gives a broader, flatter line across the UV region.

    Figure 10: QUV (A) Weathering of Blue Tint PVDF Coil Coating

    Tailor-Made Advances in Inorganic Pigments

    Cobalt-based pigments can be described in chemical terms using the generic name "mixed metal oxide" pigments. This class of high-performance colorants offers excellent chemical and thermal stability, and compatibility with most resins systems to give unsurpassed performance. Since these pigments are produced by a high-temperature solid-state reaction of metal oxides or salts, they are able to withstand any temperature encountered during processing or application or the product. As shown in Figure 7, mixed metal oxide pigments act as UV opacifiers, effectively scattering UV and visible light away from the surface of the coating.

    Figure 11: QUV (A) Weathering of Blue-Green Tint PVDF Coil Coating
    New cobalt blue and cobalt blue-green pigments have been developed to enhance the UV absorption and therefore the long-term durability imparted to the substrate, denoted here as second-generation pigments. Cobalt chrome aluminate blue-green pigments are the most absorptive, transmitting less than 0.1% light in the UV region (see Figure 8).

    The excellent absorptive properties of the second-generation cobalt pigments can be explained by the particle size distribution; the fine and mono-dispersed nature of these pigments explain why the visual and UV opacity can be adapted by sophisticated processing techniques to achieve tailor-made pigments (see Figure 9). The UV opacity benefits, predicted by UV transmission thin film testing in PVDF coil coating, have been verified by subjecting PVDF panels to accelerated QUV(A) weathering (see Figures 10-11).

    Figure 12
    Although the performance of cobalt pigments largely remains undisputed, the coloring cost is higher than other alternatives, therefore offering performance at a price. The second generation offers the benefit of enhanced performance with enhanced tinting strength, hence a lower coloring cost, thereby providing an attractive coloring option to the formulator (see Figure 12).

    Conclusion

    With the market increasingly moving toward super-durable coatings, the pigment component has an important role to play, not simply for coloration, but in providing protection against harsh climatic conditions. This article addresses the mechanisms for binder degradation and protection offered by the pigment, demonstrating that the functionality of inorganic pigments can be tailored to achieve excellent durability. The surface coater therefore can have greater confidence with the industry requirements of long lifetime guarantee.

    This paper was presented at the European Coatings Show, Nurenburg, April 2001.

    For more information on inorganic pigments, contact Johnson Matthey Pigments and Dispersions, 11400 New Berlin Road, Jacksonville, FL 32226; phone 800/770.2634; fax 904/751.6828; Helen Hatcher, New Product Manager, e-mail hatchha@matthey.com; Andrew Tocher, Applications Technologist, e-mail tochea@matthey.com; or Circle Number 61.

  • Share This Story

    Looking for a reprint of this article?
    From high-res PDFs to custom plaques, order your copy today!

    Recommended Content

    JOIN TODAY
    to unlock your recommendations.

    Already have an account? Sign In

    • PCI-0724-Global10-Feature-1440.png

      2024 Global Top 10: Top Paint and Coatings Companies

      Who ranks on top? PCI’s annual ranking of the top 10...
      Global Top 10 and PCI 25
      By: Courtney Bassett
    • PCI-0724-PCI25-Feature-1440.png

      2024 PCI 25: Top Paint and Coatings Companies

      PCI's annual ranking of the top 25 North American paint...
      Global Top 10 and PCI 25
      By: Courtney Bassett
    • pci1022-Kinaltek-Lead-1170.jpg

      A Novel Pigment Production Technology

      Following an extensive R&D program that demonstrated...
      Paint and Coating Pigments
      By: Jawad Haidar and Nitin Soni
    You must login or register in order to post a comment.
    Unable to fetch comments.

    Report Abusive Comment

    Manage My Account
    • eMagazine
    • eNewsletter
    • Online Registration
    • Subscription Customer Service

    The Coatings Minute: Print Returns with PCI’s New Showcase Issue

    The Coatings Minute: Print Returns with PCI’s New Showcase Issue

    The Coatings Minute: Why Industry News Matters More Than Ever

    The Coatings Minute: Why Industry News Matters More Than Ever

    The Coatings Minute: Your Inside Look at PCInnovations

    The Coatings Minute: Your Inside Look at PCInnovations

    CTT Registration Now Open

    CTT Registration Now Open

    More Videos

    Sponsored Content

    Sponsored Content is a special paid section where industry companies provide high quality, objective, non-commercial content around topics of interest to the PCI audience. All Sponsored Content is supplied by the advertising company and any opinions expressed in this article are those of the author and not necessarily reflect the views of PCI or its parent company, BNP Media. Interested in participating in our Sponsored Content section? Contact your local rep!

    close
    • Modern arapartment complex painted in bright colors.
      Sponsored byEPS - Engineered Polymer Solutions

      Architectural Polymers Leading the Way in Coatings Innovation

    • paint sprayer in a workshop
      Sponsored byallnex

      Enabling Performance and Compliance: allnex Introduces a New Line of VOC Exempt Solvent-Borne Resins

    Popular Stories

    No. 3 AkzoNobel

    AkzoNobel to Close Two Manufacturing Sites

    Modern living room interior with green plants, sofa and green wall

    Reimagining Architectural Paints with Plant-Based Acrylic Binders

    Modern arapartment complex painted in bright colors.

    Architectural Polymers Leading the Way in Coatings Innovation



    PCI Buyers Guide

    Submit a Request for Proposal (RFP) to suppliers of your choice with details on what you need with a click of a button

    Start your RFP

    Browse our Buyers Guide for manufacturers and distributors of all types of coatings products and much more!

    Find Suppliers

    Events

    September 3, 2025

    Coatings Trends & Technologies Summit

    The Coatings Trends & Technologies (CTT) Summit is an annual conference for both liquid and powder coatings formulators and manufacturers to discuss innovations in coatings technology. This event combines high-quality technical presentations, a resource-rich exhibit hall, and dedicated networking opportunities to connect scientific minds, foster innovation, and cultivate game-changing new ideas!

    January 1, 2030

    Webinar Sponsorship Information

    For webinar sponsorship information, visit www.bnpevents.com/webinars or email webinars@bnpmedia.com.

    View All Submit An Event

    Poll

    Longest-running laboratory experiment

    What is the longest-running laboratory experiment?
    View Results Poll Archive

    Products

    CTT Summit Short Courses (Live 9/3/25)

    Coatings Trends & Technologies Summit is expanding its offerings with four short courses. These short courses will offer an extensive day of interactive learning.

    See More Products
    pci  webinar april 2025

    PCI CASE EBOOK

    Related Articles

    • Shepherd

      Shepherd Highlights High-Performance Inorganic Pigments and Ink-Ready Dispersions

      See More
    • Progress in the Field of Yellow Organic Pigments for High-Performance Applications

      See More
    • New Generation of Silica-Encapsulated, Ultramarine Blue High-Performance Pigments for Coatings

      See More

    Related Products

    See More Products
    • durability.jpg

      Increasing the Durability of Paint and Varnish Coatings in Building Products and Construction 1st Edition

    See More Products

    Events

    View AllSubmit An Event
    • March 5, 2025

      Fibrillated Cellulose Boosts Mechanical, Surface & Rheology Performance of Elastomeric Roof Coatings

      On Demand The topic of this webinar will be the use of Valida fibrillated cellulose in Elastomeric roof coatings.
    View AllSubmit An Event
    ×

    Keep the info flowing with our eNewsletters!

    Get the latest industry updates tailored your way.

    JOIN TODAY!
    • RESOURCES
      • Advertise
      • Contact Us
      • Directories
      • Store
      • Want More
    • SIGN UP TODAY
      • Create Account
      • eMagazine
      • eNewsletters
      • Customer Service
      • Manage Preferences
    • SERVICES
      • Marketing Services
      • Reprints
      • Market Research
      • List Rental
      • Survey & Sample
    • STAY CONNECTED
      • LinkedIn
      • Facebook
      • Youtube
      • X (Twitter)
    • PRIVACY
      • PRIVACY POLICY
      • TERMS & CONDITIONS
      • DO NOT SELL MY PERSONAL INFORMATION
      • PRIVACY REQUEST
      • ACCESSIBILITY

    Copyright ©2025. All Rights Reserved BNP Media.

    Design, CMS, Hosting & Web Development :: ePublishing

    Painting & Coating Industry (PCI) logo Powder coating summit logo
    search
    cart
    facebook twitter linkedin youtube
    • Sign In
    • Create Account
    • Sign Out
    • My Account
    Painting & Coating Industry (PCI) logo Powder coating summit logo
    • NEWS
      • Latest News
      • Market Trends & Reports
      • Price Alerts
      • Subscribe to eNewsletters
      • Global Top 10/ PCI 25
      • Weekly Featured Article
      • COATLE Word Game
    • PRODUCTS
      • Product News
      • Must See Products and Services
    • MATERIALS
      • Additives
      • Resins/Polymers
      • Pigments
      • Equipment
      • Distributors
    • TECHNOLOGIES
      • Adhesives
      • Architectural Coatings
      • Industrial Coatings
      • Nanotechnology
      • Powder Coatings
      • Solventborne
      • Special Purpose Coatings
      • Sustainability
      • UV Coatings
      • Waterborne
      • FINISHING
        • Finishing News
        • Finishing Technologies
        • Finishing Equipment
      • RESOURCES
        • Columns
          • Ask Joe Powder
          • Did you know?
          • Distribution Dive
          • Focus on Canada
          • Formulating With Mike
          • Innovation Insights
          • Moody's Coatings Conundrums
          • Powder Coating Perspectives
          • Target the Market
          • TiO2 Insider
        • Blogs
          • Editor's Viewpoint
          • Industry Insights
        • Coatings Supplier Handbook
        • Podcasts and Videos
          • COAT-IT! Podcast
          • Videos/PCI TV
        • PCI Store
        • eBooks
        • Sponsor Insights
        • White Papers
        • COATLE Word Game
      • EVENTS
        • Coatings Trends & Technologies Summit
        • Paint and Coatings Academy
        • Webinars
        • Calendar of Events
        • Lifetime Achievement Award
      • DIRECTORIES
        • Buyer's Guide
        • Equipment Directory
        • Materials Directory
      • EMAGAZINE
        • Current Issue
        • eMagazine Archive
        • China Issue Archive
        • Editorial Advisory Board
      • CONTACT
        • Contact Us
        • Advertise
        • Subscribe to eMagazine
        • Subscribe to eNewsletters