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Project Correspondence ArchiveTopic: Test Plan Input
[originally sent 6/1/99] Thank you for speaking with me this morning. I would like your steering committee to consider PPG's participation in the follow-on study to find non-chrome conversion coating replacements for aluminum alloys. PPG has a commercial non-chrome conversion coating for aluminum alloys that contains no heavy metals or VOCs, is biodegradable and cost about the same as a traditional chrome conversion coating. Our product is called ROCC (TM) which stands for Reactive Organic Conversion Coating. ROCC(TM) deposits a thin inorganic/organic film on aluminum that promotes topcoat adhesion; it's performance in a number of tests has been equal to a Cr(VI) conversion coating. The first ROCC started using the product almost 3 years ago and to date there are about 10-12 customers (the most noteworthy is Bombardier in Canada, the maker of Ski-Doos and Sea-Doos). I will gladly forward technical data sheets, material data safety sheets and various reports and papers at your request. I can be reached by e-mail at jmcintyre@ppg.com or by telephone at 216-486-5300.
Sanchem SafeGard CC-7000 was tested for salt-fog corrosion resistance in a recent Air Force study. Contact person is John Spivey, Tyndall AFB, (850) 283-6203
I was wondering if the newer chromate free coatings should have abrasion resistance examined since several have organic and polymeric constituents/components.
These conductive polymers can potentially replace CCC, reduce HAP's and VOC's associated with current coating systems and applications.
Contact is Pinakin Patel at 704.331.7236
Paul, We held a UTC-wide chromate replacement workshop on January 25 to gather our collective input for the chromate replacement project. The recommendations below were collected from the fourteen workshop participants representing four UTC companies. The names, affiliations and email addresses of the participants are appended to this note. Please feel free to add the names of the additional UTC team members to your email distribution list for the project. Control Samples In addition to the Alodine 600 and 1200 controls, we request that a "no rinse" chromate system (Permatreat 686A from Betz Metchem) and that a chrome phosphate system be included in the study. No-rinse coatings are required for certain products (airframes, vehicles etc) and do not produce wastewater from rinsing. Chromated control samples are needed to evaluate the performance of non-Cr, n0-rinse coatings. Chrome phosphate conversion coatings are widely used in non-aerospace durable goods applications. Inclusion of chrome phosphate treated controls will allow direct comparisons to be drawn with the candidate non-Cr systems. In addition to the base metals list, we request the inclusion of 5052 and 1100 Al, G90 galvanized steel and 1010 steel. Rationale 5000-series alloys are widely used in UTC products and other applications such as armored fighting vehicles. 1100 Al is widely used in the HVAC industry for heat exchanger fins and, due to its high purity, is a good surrogate for IVD, Alclad and other surface aluminizing treatments. We request that dry-in-place conversion coatings be included in the study. We request that MacDermid's Chemidize 727 be included in the study. We request that S-Poly coating samples be tested. We request that vacuum and ion-beam deposited and thermal spray processes be removed from the scope of the study. Rationale Dry in place coatings are widely used and have inherent environmental benefits. Chemidize 727 has produced favorable test results in some internal tests. S-Poly coatings are an emerging technology that demonstrates exceptional (2000 + hrs for scribed 2024 Al ) salt fog performance. Thermal sprayed and vacuum and ion-beam deposited coatings are not viewed as drop-in replacements and represent a significant level of process complexity that will dilute effort and impede the progression of work. We request that scribed, painted samples be exposed for 2000 hours to ASTM B117 salt fog conditions. These samples should be coated with a white, unprimed TGIC polyester powder paint to a thickness of 1.8-2.2 mils. The samples should be equipped with four stainless steel through-hole fasteners. We request that a standardized approach to panel scribing, i.e., "V" notch or rectangular, be discussed and adopted to reflect current best practices. We request that electrochemical impedance spectra be collected on painted samples after 28 day salt water immersion We request that a rationale for the proposed DC polarization testing be presented. We request that the 2-week salt spray test be omitted. We request that two additional adhesion tests be performed: ASTM D4541 (on panels at least 1/8" thick) and an instrument based "knife removal" test of coating bond strength. We request that the TGIC polyester powder paint referenced above be included in the adhesion test plan. We request that real-life exposure testing, paint and bake, and reworkability tests be omitted. We request that certain data be acquired from all coating suppliers including coating and bath QC procedures, and detailed information on panel pretreatments, coating weight and post treatments. Rationale Most product applications of conversion coatings are in conjunction with organic coatings. Coated panels weather differently than bare panels due to geometric effects and interactions with the conversion coating at the interface. A low-cost, widely used powder coating polyester powder coat will allow for an assessment of the conversion coating's contribution to system durability without undue influence from inhibitive primers or other performance additives common to mil-spec paints. The inclusion of fasteners on the panels will allow for the assessment of crevice and local galvanic effects. Scribed panel notch geometry is a controversial issue that is the subject of current work in the aerospace community. The best practice for reproducibly and credibly scribing panels should be used. We have found that impedance testing as described can detect conversion coating / paint interactions that result in a loss of barrier properties. We do not now understand DC polarization tests to be relevant to the evaluation of conversion coatings. The additional adhesion tests will provide quantitative bond strength information that can be directly assessed for product applications. The inclusion of a TGIC polyester powder coating will make the study's results relevant to the commercial sector. We believe that real-life exposure testing and paint and bake testing should be done to company specifications during "qualification" rather than "screening" testing. We believe that reworkability tests will add significantly to the complexity of testing to an extent that outweighs the information delivered. Sincerely, Mark Jaworowski For the 4C's Chromate Workshop Team: Todd Bruer P&W BREUERTO@pweh.com Jerry Golden UTRC goldengs@utrc.utc.com Dick Grannells Hamilton Standard GRANNEL@hsd.utc.com David Grulke Hamilton Standard GRULKED@hsd.utc.com Mark Jaworowski UTRC Jaworomr@utrc.utc.com Joe Lee Carrier Joseph.Lee@carrier.utc.com Kelly Loch Carrier Kelly.Loch@carrier.utc.com Bob Melnick Sikorsky rmelnick@sikorsky.com Joe Parkos P&W PARKOSJ@pweh.com Tom Rose Sikorsky TCRose@sikorsky.com Blair Smith Hamilton Standard SMITHBL@hsd.utc.com Tom Swarr UTC SWARRTE@CORPHQ.UTC.COM Adam Weissman Sikorsky AWeissman@sikorsky.com Dana Welkes Sikorsky DWelkes@sikorsky.com Lee Zook USBI ZookL@usbi.com
Paul: AL9210 by CHEMAT is a pre-treatment that is of the sol-gel type. It is sold as an aqueous colloidal solution and comprises of 'organo-aluminum-silicate' compounds. It can be either used using the traditional 'dip-tank' method or it is also amenable to being sprayed. It is recommended as an alternative to anodization, but I do not see any reason why it cannot be used to replace chromated conversion coatings. On another subject, could you please also add "Fluid Resistance" as a test method in the 'other' category on your test methods page? I will try adding it myself ... but just in case. I would also be happy to help draft out an initial test plan. -Vinod
Paul; I reviewed the information contained within the site. Everything looked fine to me. My only suggestion was that perhaps the use of a no-rinse chromate conversion coating be evaluated. While this coating still contains chromium, being no-rinse prevents the majority of it from entering the natural environment (i.e., no water to treat) and still provides the level of corrosion resistance required for many Aerospace applications. The no-rinse coating that we use at Hamilton Standard is called Permatreat 686A from BetzMetchem. This coating generally provides increased corrosion resistance over typical Alodine 600 and 1200 at temperatures up to 250 °F on 2024-T3 aluminum. Painting adhesion over this coating is also equivalent to that over conventional chromate coatings. Blair A. Smith Phone: (860) 654-4081 Fax: (860) 654-5453 e-mail: smithbl@hsd.utc.com
Paul, Pretty good idea to use the web site as your central communication tool. This should work very nice. Here are my first comments for coatings, substrates, and tests. Substrates - Include the temper designation for the alloys. For example: 7075-T6, 2024-T3, 6061-T6, 356.0-T6, etc. Coatings - Include all steps or chemicals required for the coatings. For example, Sanchem CC-3000 required boiling water, CC-3000 and CC-4000 to form the conversion coating on a piece of clean/deoxidized aluminum. We need to know how many new tanks are required to replace the one tank chromate conversion coating process. Tests - Include as much detail about the tests as possible. Also identify what paints will be tested for paint adhesion (water based, solvent based, chromated, nonchromated). I will add my ideas to your web site and try to clarify some of these issues. Steve Gaydos
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