Tackling a transportation center or high-traffic, urban project? Consider corrosion-resistant finishes

FL-Orlanda-ITF-stretchforming (2)-courtesy of Acurlite

Orlando International Airport’s South Intermodal Terminal Facility.  Photos courtesy of Acurlite

Transportation facilities, transit oriented developments and other high-traffic city centers provide the connecting points and places that compose our urban landscapes and skylines. They also can present significant challenges in protecting exterior-facing architectural aluminum products. Without proper precautions and finishes, corrosion to finished aluminum components ultimately can damage the structural integrity of the building envelope and can lead to systemic failure.

 

Windows, storefronts, entrances and curtainwalls, sun shades, canopies, skylights, column covers, rain screens and exterior panels all commonly are manufactured from aluminum and integrally connect to a building’s façade. In almost any city, these architectural aluminum products are continually exposed to not only weathering, but to pollution and chemicals, as well as bumps and scuffs of pedestrians. While salt spray performance considerations usually are reserved for coastal conditions, it’s important to remember that salt mixture often is used to de-ice roads making it an equal concern in colder climates.

As a prominent part of the building’s exterior, the finished aluminum adds color and design to the project; this coating also protects the building from unsympathetic surroundings. The American Architectural Manufacturers Association (AAMA) continues to set the highest standard for architectural finishes, especially in highly corrosive environments. When selecting a coating that will be required to withstand such conditions, select either the highest-performing organic paint coating that meets the AAMA 2605 specification, or a Class I anodize that meets AAMA 611.

Orlando-_-ITF-webHigh-Performance Painted Coatings

High-performance, 70 percent polyvinylidene fluoride (PVDF) resin-based coatings give architects, specifiers and building owners the capability to select nearly any conceivable color or combination of colors, while shielding the building against weathering, pollution and aging.

PVDF is known for its exceptional chemical stability and excellent resistance to ultraviolet (UV) radiation. It is used in architectural applications as a coating on aluminum where it provides exceptional resistance to environmental exposure.

Cedar Avenue Transit Station-2

Minnesota’s Cedar Grove Transit Center Photos courtesy of Protean Construction & Mark Long

The carbon-fluorine bond, used in the 70 percent PVDF, including Kynar® 500 resin-based architectural coatings, is one of the strongest bonds known. These paint coatings can withstand enduring and intense UV radiation. Such attributes support long-term color- and gloss-retention, and chalk-resistance.

 

These highest-performing 70 percent PVDF coatings meet the most stringent, exterior, architectural specification AAMA 2605, “Voluntary Specification for High Performance Organic Coatings on Architectural Extrusions and Panels.” This specification requires paint coatings to meet rigorous testing performance standards including more than 4,000 hours of salt spray, and heat- and humidity-resistance.

Protean - Cedar Grove TransitCorrosion-Resistant Requirements

Section 8.8 of AAMA 2605 refers to the corrosion resistance requirements of all coatings that must pass these stringent guidelines:

  • Humidity –The sample is exposed in a controlled heat and humidity cabinet for more than 4,000 hours at 100 degrees Fahrenheit and 100 percent relative humidity. No formation of blisters to extent greater than “few” blisters, as defined by ASTM D714.
  • Cyclic corrosion testing (previous referred to as salt spray resistance) – Score the film sufficiently deep to expose the base metal. Expose the sample for 2,000 hours according to ASTM G85, Annex A5, dilute electrolyte cyclic fog/dry test. The sample must score a minimum rating of 7 on scribe or cut edges and a minimum blister rating of 8 within the test specimen field, as defined in ASTM1654.
  • South Florida exposure – The coating shall maintain its film integrity, color retention, chalk resistance, gloss retention and erosion resistance properties for a minimum of 10 years on the south Florida on-fence testing site.
  • Color retention – Maximum of 5ΔE Units (Hunter) of color change after the minimum 10-year exposure test. A ΔE unit is the variance or color difference measured on a vector scale from a specific point in the color space.
  • Cedar Avenue Transit Station-1 399X440 Duranar MICAChalk resistance – Chalking shall be no more than that represented by a No. 8 rating for colors and No. 6 for whites after 10 years of test fence exposure. Per ASTM D4214, chalking is measured on a numerical scale with higher numbers representing better chalk resistance.
  • Gloss retention – Gloss retention shall be a minimum of 50 percent after the 10-year exposure testing, as described by ASTM D 523.
  • Resistance to erosion – Less than 10 percent film loss after the 10-year exposure testing
  • AAMA notes that high humidity environments such as, but not limited to, seacoast or industrial environments, performance of corrosion resistance may be diminished.

 

Metro Transit shelter

Metro Transit’s New BRT Shelters Photos courtesy of Duo-Gard

High-Performance Anodize Finishes

 

Class I anodize finishes that meet or exceed all requirements of AAMA 611 “Voluntary Specification for Anodized Architectural Aluminum” also resist the ravages of time, temperature, corrosion, humidity and warping. Anodized aluminum withstands extreme temperature changes and weather conditions, constant exposure to vehicle exhaust, and daily use by passengers. Over-sprayed salt de-icing can be managed with a simple rinsing as needed. With basic cleaning and maintenance, architectural aluminum products enjoy a long life cycle.

Metro shelte3The anodizing process, because it is an integral part of the substrate, produces an oxide film that is uniform, hard and protects the rest of the aluminum substrate from deterioration – providing excellent wear and abrasion resistance. The coating produced is extremely durable, and the hardness of the surface is comparable to a sapphire—the second hardest substance on earth. This characteristic makes anodize an ideal choice for use in high-traffic areas where resistance properties are important.

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New York’s The Forge.   Photos by Arch Photo, Inc., Eduard Hueber

In the most challenging applications, anodize aluminum will perform as specified and will not reduce the service life of the aluminum, but may affect the natural beauty of the surface finish. Avoid any conditions that quickly can corrode an anodize finish such as mortar, cement and other alkaline materials.

To meet AAMA 611 requirements, Class I anodize must have a dry film minimum thickness of 0.7 mils to pass these stringent guidelines:

  • Abrasion Resistance (Michael Clarke Test) – A go/no-go abrasion test using abrasive papers coated with silicon carbide, garnet and glass, respectively. This is used to discriminate between films of the correct hardness and those that may give poor service because they are too soft. The specification grade of abrasive paper is Abrasive Type: Glass, Grade: “Flour,” Mohs’ Hardness Scale Number: 4.5-5.5.
  • Corrosion Resistance testing (previous referred to as salt spray resistance) –Expose the sample for 3,000 hours according to ASTM B117 using 5 percent salt solution. Test samples shall show no more than a total of 15 isolated spots or pits none larger than 1 mm in diameter, in a total of 381 cm of test area grouped from five or more test pieces.
  • South Florida exposure – The coating shall maintain its color retention, gloss retention and erosion resistance properties for a minimum of 10 years on the south Florida on-fence testing site.
  • Color retention – Maximum of 5ΔE Units (Hunter) of color change after the minimum 10-year exposure test.
  • Gloss retention – Gloss uniformity shall be within established gloss range.

 Durability and Sustainability

TForge_018-webAnodized aluminum is an inert, non-combustible material that is 100 percent recyclable and poses no health risks. At the beginning of the new millennium, Linetec and other environmentally responsible finishers, changed from the traditional caustic etching process to a more eco-friendly etch system allowing customers to use secondary (recycled) billet in the anodize process.

Small surface defects, such as those common in recycled material, are hidden by the eco-friendly anodize finish’s “frosty” matte appearance. Architects prefer the aesthetic of this matte finish. The resulting surface also reduces glare in bright sunlight. Gloss level reading is typically reduced from 15 to 25 with conventional anodize, down to a gloss level of 3 to 12 for eco-friendly color anodize.

The eco-friendly anodize process reduces landfill waste used with conventional etch processes by 75-80 percent. Landfill waste directly relates to the production of greenhouse gas. It also has the viscosity of water and will not collect in the small recesses of aluminum extrusions or narrow aluminum tubes, which enhances the durability and lifecycle of the finished architectural aluminum product.

cedar-ave-transit-berg-170607-8198-o.jpgFor painted architectural aluminum products, Linetec and the leading paint manufacturers recommend the use of a PVDF-based paint system on aluminum material for all corrosive environments. Offering the longest lifecycle, a 70 percent PVDF resin-based coating system, pretreated with chrome phosphate, along with an inhibitive chrome-rich primer should be used. This coating type meets or exceeds all the requirements of AAMA 2605.

Beyond ensuring the highest quality application, Linetec also is recognized as an industry-leading environmentally responsible finisher. It also captures the liquid paints’ volatile organic compounds (VOCs) content using a 100 percent air capture system and safely destroys the VOCs with a regenerative thermal oxidizer. Linetec then re-uses its heat energy byproduct to improve process energy efficiency. This process of re-use is completed before the material exits the paint line.

LinetecBrushedStainlessAnodize-web3Specification and Selection

To ensure the finish specified on your project’s architectural aluminum products contribute to its long life, durability and sustainability, download a free PDF of “Section 05 0513 Shop Applied Coatings for Metal 3-part Guide Specification.”

For personalized assistance in selecting the finish for your next transportation or high-traffic project, please contact us and we’ll be happy to assist you.

 

“Going Green on the Green” highlights energy-efficient windows finished by Linetec

CT-195CHURCH_WoodruffBrown09-web“Window retrofit increases energy efficiency, occupant comfort and savings,” reports Commercial Architecture magazine in describing 195 CHURCH’s renovation. Supporting these achievements, Linetec’s anodize finish also enhances the windows’ durability, minimizes maintenance and maximizes longevity.

Located on the New Haven Green in Connecticut, the 244,000 square foot, 18-story, Class A office building was built in 1974 and is largely constructed of concrete. The original windows remain functional, but were manufactured at a time before low-e insulated glass and improved thermal breaks in the aluminum framing were available.

Helping the property manager select the optimal window system, Apogee Enterprises, Inc.’s Building Retrofit Strategy Team provided an annual energy savings forecast showing the potential savings offered by Wausau Window and Wall Systems’ S.E.A.L. interior accessory windows. These units install from the building’s interior over existing, weather-tight windows to improve thermal and acoustical performance.

The windows’ extruded aluminum frames were finished by Linetec in Dark Bronze anodize to meet the requirements of the American Architectural Manufacturers Association’s stringent Class I specification standard, AAMA 611. The anodized aluminum resists the ravages of time, temperature, corrosion, humidity and warping for a long product life cycle.

CT-195CHURCH_WoodruffBrown06before-webMore than 1,400 new energy-efficient window inserts, in combination with 9,000 new LEDs, are anticipated to save 195 CHURCH’s owners 29 percent in annual electrical energy consumption and are on track to significant earn a rebate from the utility provider.

Download the full case study on this and other renovation projects from Apogee’s web page.

For personalized assistance in selecting the finish or thermal improvement services for your next project, please contact us and we’ll be happy to assist you.

Construction Specifier column addresses “Avoiding Color Variation with Anodize Finishes”

champagne range sample

Linetec Champagne anodize range sample

Learning from failures are some of the most difficult and most valuable lessons. Many times, failures can be avoided if we turned to those with more experience for advice. The Failures column in the January issue of Construction Specifier takes this approach issue and shares advice on “Avoiding Color Variation with Anodize Finishes.”

Authored by Linetec’s Tammy Schroeder explains the variables affecting color in the anodize process, and the challenges of achieving an exact color from run to run and load to load.

To minimize color variation, she offers five tips:

  1. Maintain metal consistency – The easiest way to ensure this is to work with one metal source/extruder per project and request all metal come from one lot of material.
  2. Do not mix aluminum alloys, as even mixed tempers will not produce uniform results – For best results, use 6063 alloys for extrusions and 5005 for flat sheet stock and fabricated parts. When structural alloy is required, 6061 and 5052 can be used, but will not give similarly acceptable results.
  3. Perform as much bending and forming as possible prior to finishing – Anodic films are very hard, and as a result most post-production bending causes the film to “craze,” which produces a series of small cracks in the finish, giving it a spider-web like appearance.
  4. Be aware of anodizing’s effect on welds – The heat developed from the welding process changes the metallurgy on nearby metal or heat-affected zones, causing localized discoloration (i.e. halo effect), so one should use the proper 5356 alloy welding wire and lowest heat possible.
  5. Select an anodizer that uses automation – This helps to reduce inconsistencies in the process.
dark bronze range sampeles

Linetec dark bronze anodize range samples

Click here to read the whole Failures column, and please contact us for personalized service in avoiding color variation and selecting the correct finish for your next project.

How do you clean anodized aluminum?

CherryAirport09Anodized architectural finishing gives a tough and long-lasting surface to aluminum. This is particularly useful for high-traffic areas of a building, where hardness and abrasion resistance is vital. While anodize is as hard as sapphire (the second hardest substance in the world), it still requires regular maintenance and care.

Although anodized aluminum is exceptionally resistant to corrosion, discoloration and wear, it can be marred by harsh chemicals, abuse or neglect. Periodic maintenance inhibits long-term accumulation of soil, which can accelerate weathering of the finish.

It depends on the weather

The environment of the building will influence the cleaning frequency your anodized surfaces require. Factors such as smog, condensation or low rainfall areas can contribute to a surface needing more frequent cleanings to remove salt and dirt build-up. Areas that have seasonal rainfall to help remove water-soluble deposits and soil will require cleaning less often.

TampaMuseumofArt-close-up-webIt depends on the placement

Regardless of climate, recessed and sheltered areas usually become more heavily soiled because of the lack of rain-washing. Overhangs, bottoms of fascia panels and sheltered column covers are particularly susceptible to soil build-up. If not addressed, this can lead to accelerated weathering of the anodized finish. Integrating this as part of the building’s overall maintenance schedule is the most efficient and economical way to make sure soil and salt build-up is kept in check.

It depends on the build-up

The severity and tenacity of the soil build-up will determine progressively stronger cleaning procedures that can help maintain a building’s anodized surfaces. Be cautious. Experiment on a small area of the building, using stronger methods until you find the one that works.

  • For light soil, flush the surface with water using moderate pressure. Let it air dry and check to see if the build-up still remains.
  • If the build-up remains, move to scrubbing with a brush or sponge while spraying with water.
  • If, and only if, that does not remove the build-up, then add a mild detergent cleaner to the scrubbing.
  • If heavy surface soil persists, add an abrasive cleaning pad to the mild detergent washing. Be sure to always scrub in the direction of the metal grain.
  • If detergent is used, rinse the surface thoroughly, multiple times, with clean water after scrubbing, to avoid detergent residue building up in place of soil.

It depends on the cleaner

Methyl ethyl ketone (MEK) or similar solvents should only be used to remove oil, wax, polish or similar material from your surface. Extreme care must be exercised to keep MEK from damaging any organic sealants, gaskets and finishes around anodized surfaces. If the anodize is protected with a clear, organic coating, do not use MEK solvent, as it may deteriorate or remove the coating completely. Do not use aggressive alkaline or acid cleaners on or near anodized aluminum.

It depends on deterioration

Even if well maintained, architectural finishes, including anodize, could eventually need repair. There are solutions for both minor and major damage and deterioration of anodize, so plan accordingly. For small scratches and rub marks, minor touch-up paint can be used. The paint should closely match the color of the factory-applied anodize finish. Use caution when applying touch up paint to the damaged area. Be aware that the touch-up paint will not be as hard as the original finish and is not intended for areas larger than a few square inches.

harsh-chemical-damage-webWhen larger anodized areas are damaged beyond what a simple touch-up can fix, it is time to call in a professional. Large, full-service finishing companies often employ field service workers who are able to prepare and apply architectural paint finishes in the field. The coating used should meet the American Architectural Manufacturers Association’s AAMA 2605 specification and be tinted to match the existing finish. This can be a difficult goal, particularly if only a portion of the existing surface is being refinished or the finish has already experienced some fade. Be certain to ask for an onsite sample to approve of before the full project begins.

Learn more about anodizing and its care and maintenance by clicking here. For personalized assistance in selecting or repairing anodize finishes for your aluminum building products, please contact Linetec’s regional sales managers, email sales@linetec.com or call 888-717-1472.

Slate, Portland’s new, LEED Gold, mixed-use, transit-oriented development features Linetec’s paint, anodize and thermal improvement services

OR_Slate_9267JoshuaJayElliott-courtesyWorksProgressArchitectureLLPwebThe 10-story, LEED® Gold certified, mixed-use, transit-oriented development known as Slate is helping revitalize the Burnside Bridgehead area in Portland, Oregon. Formerly a vacant lot called Block 75, the new building features window, entrance, unitized curtainwall and panel systems finished by Linetec. Contributing to the building’s high energy-efficiency and sustainability goals, Linetec also provided the thermal improvement services for the glazing systems’ aluminum framing.

Opened last year, the project spans 147,000 square feet and offers 75 market-rate apartment units on the upper six floors; 35,000 square feet of creative co-working office workspace on floors 2-4; and 7,800 square feet of retail space at street level.  read more

 

Anodize Nickel Test

Linetec-dark-bronze-Ano-nickel-rub-2blue-web

Nickel Test

When extreme hardness is required for aluminum building components, such as in high-traffic areas, like entranceways and railings, an AAMA 611-14 anodized aluminum finish should be specified.

The hardness of anodized aluminum rivals that of the diamond.

This “Nickel Test” demonstrates why a Class I high-performance anodize coating is the perfect choice for exterior architectural applications.

How does aluminum become anodized?

LinetecAnodize_web-300dpiAnodizing is the most durable and long-lasting option for finishing architectural aluminum building products. An electrochemical process, anodizing produces a finish that resists the ravages of time and environment. However, there are important things to note about color selection for anodized aluminum.

Linetec’s two-step electrolytic anodizing process , where the anodizing and coloring of the aluminum occur in two separate steps, involves:

  • first placing the aluminum in a solution of sulfuric acid and water, then charging it with electrical current to form aluminum oxide on the surface.
  • then after anodizing is complete, parts can be immersed in a bath containing an inorganic metal such as tin, cobalt or nickel, which is deposited in the anodic pores to achieve color.

anodize-ring2-webAs a result, anodized finishes’ color choices range from clear to champagne to a variety of bronze tones to black. Linetec also offers a copper anodize, which involves an additional color tank, using actual copper to color the aluminum while isolating the copper in the coating. This process makes the copper color very stable and consistent.

Anodic oxide is not affected by ultraviolet light and is resistant to scratches, which help ensure color stability.

Due to the chemical process used to create an anodized finish, the possibility of color variation can be a concern during its application. Here are some factors to keep in mind to minimize the variation from your desired color:

  • Single source it. While the aluminum is anodized during the process, other metals (silicon, zinc, magnesium, etc.) present in the aluminum alloy can respond differently, resulting in unwanted variation of color. Reduce this risk by having all metal used for a project come from a single source/extruder, and from one lot of material. Also, avoid using aluminum with different alloys, as it will not yield uniform results.
  • Request a range sample. Because it is impossible to know the effect non-aluminum metals in the material will have on the final product’s color, be sure to ask your anodizer for a range sample before sending them your product for finishing. An anodize range sample is two anodize color chips for the same color, with one showing the lightest extreme of appearance to be expected on the finished parts and one showing the darkest. Be aware that the lighter the anodize finish, the more noticeable the range. Be sure to speak with any potential anodizer to see what range of variation they can guarantee. AAMA’s industry-leading standards specify that the range should not differ by more than 5 Delta E. A quality anodizer may be able to keep the range of a color even lower.
  • Bend then finish.  Anodic films are very hard, and as a result, most post-production bending causes a series of small cracks in the finish that give it a spider-web appearance. To avoid this, have as much bending and forming of the material completed before it is sent to receive its finish.
  • Weld with care.  If your metal has any welds on it, the anodization process can cause a halo effect of localized discoloration around them. Welding with the proper 5356 alloy welding wire and the lowest heat possible helps minimize this.

Select an aluminum finisher that utilizes automation in its anodize process to reduce inconsistencies. An automated system controls and monitors the process, including tank sequencing, chemical add, voltage, current, time and temperature, which ensures the most consistent anodize finish possible.

Learn more about anodizing by clicking here. For personalized assistance in choosing an anodize color for your aluminum building products, please contact Linetec’s regional sales managers, email sales@linetec.com or call 888-717-1472.