Grantee Research Project Results

Final Report: Environmentally Friendly Anti-Corrosion Coatings

EPA Contract Number: 68D00244
Title: Environmentally Friendly Anti-Corrosion Coatings
Investigators: Miller, Michael B.
Small Business: Luna Innovations Inc.
EPA Contact:
Phase: I
Project Period: September 1, 2000 through March 1, 2001
Project Amount: $69,974
RFA: Small Business Innovation Research (SBIR) - Phase I (2000) RFA Text |  Recipients Lists
Research Category: Nanotechnology , SBIR - Pollution Prevention , Pollution Prevention/Sustainable Development , Small Business Innovation Research (SBIR)

Description:

Corrosion of metal structures is estimated to cost billions of dollars annually. The most common methods of corrosion inhibition or prevention involve the application of heavy surface treatments (paints and primers) or conversion coatings with various metallics using processes that are strictly controlled and regulated due to toxicity and possible carcinogenic properties. The purpose of this Phase I SBIR program is to develop an alternate process that is capable of corrosion inhibition without the use or generation of hazardous materials. Luna Innovations has developed a new coating process based on ionic self-assembled
monolayers (ISAM) that has demonstrated corrosion inhibition on some aluminum alloys, neither contains nor generates hazardous materials, and 3) has demonstrated practical application methods including spraying and non-electrolytic brushing. In this program, Luna proposed to further develop the process for aluminum, and to investigate the adaptation of the coating process to steel and other metals and alloys. The ultra-thin coating layer is compatible with all typical fabrication processes including welding and painting.

Ionic self-assembled monolayers (ISAMs) are a recently developed revolutionary technique that allows detailed structural control of materials at the molecular level combined with ease of manufacturing and low cost. The ISAM method involves the alternate dipping of a charged substrate into an aqueous solution of a cation followed by dipping in an aqueous solution of an anion at room temperature. Since the adsorption is based on the electrostatic attraction of interlayer charges, each layer is self-limiting in thickness and uniform at the molecular level. This occurs because the film molecules are free to adjust their positions to improve the overall packing since they are not covalently bound to the substrate.

Sequential layers are rapidly fixed by drying at room temperature and pressure. Multilayer films several microns in thickness are easily fabricated by repeating the dipping process with no limit to the number of layers that can be deposited. The resulting pliable films are mechanically very robust and are only removed by vigorous scraping.

Test coupons of standard metals such as 2024 aircraft aluminum, 260 brass, copper, AZ91E magnesium and 1018 steel were prepared, cleaned and coated with a number of ISAM polymer and nanoparticle coatings. Electrochemical analysis was performed on laboratory sample to determine the electrochemical potentials and permeabilities of the coatings. Salt fog testing according to ASTM B117 standards was carried out on the test coupons for a period of 168 hours, after which the coupons were washed and examined for evidence of corrosion products. In addition, the primer properties of the ISAM coatings were studied by applying standard military aircraft paint, exposing the painted coupons to the salt fog test, and performing the military standard wet tape adhesion test.

Summary/Accomplishments (Outputs/Outcomes):

The results of salt fog testing on aluminum, magnesium and brass indicate significant corrosion inhibition in areas where the ISAM films were applied. Additional inhibition is evident where Laponite nanoparticles were also included
in the films. The particular ISAM films studied in this program did not prevent corrosion on steel coupons, although there is evidence that chemically terminating the ISAM films may be able to inhibit corrosion even on these metals.

The ISAM film deposition process was studied for upscaling to commercial process, and it was determined that low-cost spray-coating processes with short cycle times are feasible. Commercialization studies indicate large markets for
low-cost coatings that will provide additional corrosion inhibition using environmentally-friendly materials like the ISAM films. Experts in corrosion from industry and academia have evaluated the ISAM process and believe that it will be most useful as a corrosion inhibiting adhesion promoting film for use as an initial surface treatment or primer under more traditional surface treatments. The data from the program support this finding.

Conclusions:

ISAM fabricated film structures have the ability to inhibit corrosion on a number of common alloys of aluminum, brass and magnesium, and potentially on steel. The ISAM process is suitable for commercialization, as demonstrated by the
development of a spray process and the short coating times demonstrated in this program.

Further development of a commercial coating system based on the results of this program during a follow-on Phase II will result in a new, environmentally friendly coating process for the protection of aluminum and magnesium alloys, leading to significant cost savings and superior protection capabilities.

Journal Articles:

No journal articles submitted with this report: View all 3 publications for this project

Supplemental Keywords:

Thin film, polymer, primer, corrosion, inhibition, aluminum, magnesium, brass, steel., RFA, Scientific Discipline, Sustainable Industry/Business, cleaner production/pollution prevention, Sustainable Environment, Chemistry, Technology for Sustainable Environment, New/Innovative technologies, Engineering, corrosion resistant, environmentally benign coating, ionic self-assembled monolayers, clean technology, hazardous materials, coating processes, environmentally benign coatings, carcinogenicity, toxicity, coating formulations, alternative coatings, coatings, pollution prevention, corrsion protection