FINAL REPORT 

UV Curable Non-Chrome Primer and Advanced Topcoat System

SERDP Project WP-1520

AUGUST 2010

Dr. Thomas Phely-Bobin 

QinetiQ North America 

Distribution Statement B: Distribution 

authorized to U.S. Government Agencies only
Distribution Statement B: Distribution authorized to U.S. Government Agencies only. 

Other requests for this document must be referred to Executive Director, SERDP & 

ESTCP Office, 901 N. Stuart Street, Suite 303, Arlington, VA 22203. 
REVISED 03/24/06

Weapons Systems

and Platforms

WP-1520

Ultraviolet-Curable Non-Chrome

Primer and Advanced 

Topcoat System

Background:

Conventional coatings used by the Department of Defense

(DoD) consist of pigments for color, appearance, and

corrosion control in a polymer that serves as an organic

binder. To facilitate application, these substances are

combined with a carrier, typically organic solvents that

constitute up to 800 milligrams per liter of the coating.

Before application, surfaces have to be cleaned, usually with

solvents, and may be pretreated with a conversion coating,

mainly chromates, to protect the surface and enhance

adherence of the coatings. During application and cure,

substantial amounts of volatile organic compounds (VOC)

are released. While in service, chromates and other

hazardous components are released into the environment by

flaking and chipping of the coating.

Objective:

The objective of this project is to develop sprayable

ultraviolet (UV)-curable, corrosion-inhibiting primers and

high-performance topcoats that will provide superior

protection to aluminum substrates even when nonchromated

surface pretreatments are employed. Further, a one-coat

formulation will be developed in an attempt to combine the

corrosion-inhibiting properties of the primer and superior

durability of the topcoat into a single coating.

Process/Technology Description:

The coating system being developed is based on

Foster-Miller's patented chemistry, consisting of

formulations from oligomers of polyurethane (PU) and other

substances that are end-capped with a vinyl functionality;

reactive diluents are added to reduce viscosity. When

irradiated with UV light, photoinitiators in the mixture

generate free radicals that interact with the vinyl

functionality, resulting in the rapid, complete reaction of all

constituents, including diioscyantes, and leaving a tough,

adhesive, barrier coating. Researchers plan to develop a

compatible pretreatment/primer system from commercial

surface preparation processes and nonchromate corrosion

inhibition packages. The compatibility of the corrosion

inhibitors with the coating formulations and their effect on

the UV cure and coating performance will be evaluated.

Topcoat development will involve modifying the backbone

of the oligomers to improve performance and adding

pigments to achieve the desired appearance. After selecting

optimum formulations, full system testing will be performed

and will include testing for compatibility with existing

advanced performance coatings. The coating system will be

designed specifically for aircraft interiors and target the

coating performance requirements of the Joint Strike Fighter

(F-35) and the Joint Unmanned Combat Air System

(J-UCAS). 

Expected Benefits:

The environmentally benign coating system will have a long

shelf life, will not require premixing, and will be applied

using existing equipment. The coatings are safe to use as no

vapors or diisocyanates are released during storage or

application, and the wastes produced during depainting are

nonhazardous. Of particular relevance to the Air Force is

that the rapid UV cure will reduce the dry-to-fly time from

days to minutes. In addition, the coatings can be used for

rapid repairs in the field and are expected to substantially

reduce aircraft maintenance and hazardous waste disposal

costs. (Anticipated Project Completion - 2008)

Contact Information:

Dr. Nese Orbey 

Foster-Miller, Inc.

195 Bear Hill Road

Waltham, MA 02451 

Phone: (781) 684-4170

Fax: (781) 290-0693 

E-mail: norbey@foster-miller.com

The UV-curable, zero-VOC, single-component coating

system will have a longer shelf life.
1 / 4

UV Curable Non-Chrome Primer and Advanced Topcoat System (WP-1520)

Objective

Conventional coatings used for Department of Defense (DoD) vehicles and equipment contain

several components that are being discontinued due to their adverse health and environmental

effects. These include volatile organic compounds (VOCs), which constitute up to 800 mg/L of the

coating formulation, and hexavalent chromate anticorrosion pigments. VOCs and chromates are also

used to prepare the substrates prior to coating. These hazardous substances are released into the

environment throughout the life cycle of the coating from coating manufacture to surface preparation,

application, service life, and decoating. Containing these releases with control equipment, hazardous

waste disposal sites, and monitoring instrumentation is expensive and imposes an added logistics

burden on the military.

The National Emissions Standards for Hazardous Air Pollutants for Aerospace Manufacturing and

Rework Facilities severely curtails or eliminates the use and release of hazardous substances in

coatings. The coating industry has since produced a variety of products that are essentially free of

hazardous substances, but these new materials generally do not meet the rigorous and unique DoD

performance requirements. Consequently, coating the large fleet of U.S. military aircraft and other

vehicles continues to cost the DoD hundreds of millions of dollars each year in the procurement, use,

and disposal of toxic and hazardous materials. 

The objective of this program is to develop a family of advanced coatings that meets current and

anticipated environmental regulations and at the same time simplifies and quickens the coating

application process for military applications.

Technical Approach

Although previous versions of Foster-Miller's (FM) ultra-violet (UV)-curable polyurethane formulations

have been shown to have superior adherence and barrier properties and meet many of the

performance specifications for aircraft coatings, several issues have to be addressed for the coatings

to succeed in the intended application. A key challenge is that the coatings have not yet been used as

primers, and incorporation of anticorrosion pigments into the formulation will impede the UV cure

process and possibly have an adverse effect on other properties. In addition, although strongly

adherent and durable, the polyurethane vinyl dioxolane (PUVD) resins do not meet the new Mil-Spec

requirements for flexibility. Further, a pigment has to be introduced into the topcoat to match the

specified Federal color code, and may also hinder penetration of UV irradiation during cure. Finally,

the viscosity of the PUVD resins has to be reduced to a level suitable for DoD HVLP spray

equipment.
2 / 4

This program for the development of an advanced primer and topcoat from FM’s baseline PUVD

resins included:

Incorporating anticorrosion and color pigments and keep them stably dispersed in the

formulations.

Modifying the polymer backbone chemistry to enhance its flexibility.

Introducing additional reactive diluents into the formulation to reduce its viscosity.

Increasing the depth of cure by judicious selection of pigment type and concentration as well as

use of state-of-the-art photoinitiators and UV equipment.

Making other changes to the resin chemistry and the formulation as necessary to produce coatings

that are sprayable, cure rapidly, and meet all relevant Mil-Spec standards.

Results

Primer formulations with a range of pigment concentrations were prepared by blending anticorrosion

pigment dispersions into the baseline formulation, and adding the photoinitiators and other additives,

as required. The primers were then applied to aluminum alloy test coupons, cured, and subjected to a

preliminary set of performance and corrosion tests. Final versions of the primer contain three blends

of Sartomer reactive diluents SR489, SR506 and SR351, and could be sprayed at pressures as low

as 60 psi to produce smooth coatings 0.6 to 1.0 mil thick. All formulations showed good adhesion,

fluid resistance, impact resistance, solvent resistance, and low-temperature flexibility. It was found

that increased amounts of SR351 in the formulation increased the solvent resistance of the coating,

but decreased pigment leaching, implying less corrosion protection.

Several formulations were developed for UV-curable primers without solvents. These were successful

adhering to Sulfuric Acid Anodized (SAA) panels and in corrosion protection to those panels. The

basic PUVD resin system using reactive diluents for sprayability were found not to provide corrosion

inhibition to Chromate Conversion Coating (CCC) panels. The SAA panels have inherently more

corrosion protection relative to CCC panels. This general conclusion is made under the assumption

that the high degree of functionality of the resulting system tended to prevent mobility of the corrosion

inhibitors. It is thought that more use of exempt solvents rather than reactive diluents may eventually

work through increased mobility with the basic FM PUVD resin system. The SAA panels were

inherently more resistant to corrosion.

Much of the topcoat development was directed toward enhancing the flexibility of the baseline PUVD

formulation to meet the 40 percent elongation requirement. To this end, two new resins having

polyether modified backbones of different chain length, and a third resin with a multifunctional
3 / 4

backbone were synthesized. The resins were used either individually or in pairs, mixed in various

proportions. A concentrated white pigment containing 60 percent TiO was dispersed in reactive 2

diluent. The TiO dispersions were stable and easily blended into the resins without settling. 2

Gloss white topcoat formulations were prepared by blending TiO dispersions into the resins, and 2

photoinitiators and reactive diluent added to produce formulations containing from 20 to 30 percent

TiO . The formulations were applied on various aluminum alloy coupons using a rubber roller or draw 2

rod. Thicker coatings, up to ~2mils were cast, and in other cases the coating was applied in multiple

thin layers to obtain the desired thickness.

As expected, the baseline resin with 30 percent TiO added had good adhesion and solvent 2

resistance, but its GE Impact flexibility was only 0.5 percent. By using various combinations of the

polyether-modified resins and alternative reactive diluents, the flexibility was progressively increased

to 10 percent but with some loss of solvent resistance. Reducing the TiO level to 20 percent resulted 2 

in an increase in flexibility to 20 percent but, as a result of the lower opacity, the color of these resins

was unacceptably sensitive to coating thickness. Further trials with blends of the polyether resins and

the multifunctional resin in formulations containing 30 percent TiO produced a coating with 40 2

percent flexibility and good solvent resistance. The investigation then focused on increasing the depth

of cure to avoid the cost and time of applying the coating in multiple layers. The approach previously

developed by Foster-Miller of using pairs of photoinitiators with different absorption spectra, namely

one with a longer wavelength response for in depth cure, and one with a shorter wavelength

response for surface cure, was further pursued. Several photoinitiators were investigated, with those

having adsorption spectra extending into the visible light range proving most useful. To overcome

compatibility and other issues, different reactive diluents had to be used in combination with the

selected photoinitiator pair. It was found that good cure to a depth of ~ 2 mil could be obtained with

these photoinitiators and a resin consisting of a ~70:30 mixture of the polyether and original PUVD

resins, combined with a reactive diluent mix and a small amount of adhesion promoter. General

results found that formulations had general poor adhesion to CCC substrates while having generally

good adhesion to SAA substrates. The color matching was generally fair with poor gloss being

achieved.

Benefits

The combination of a chromate and VOC free substrate-preparation and coating system is expected

to meet the needs of a growing market that is being driven by increasingly stringent environmental

legislation. Although the UV-cure process limits the system to use by professionals, potential

applications are extensive. The baseline PUVD resin has previously been used to produce

low-observable coatings and one-coat repair formulations for military aircraft, and the availability of
4 / 4

the high-performance primer and topcoat developed here will extend this market segment to virtually

all the aerospace needs of the Air Force, Navy, commercial airlines, and NASA. In addition, the

coating system can be relatively easily tailored to meet specifications for the ground and marine

vehicles/equipment of all branches of the military. Other market segments include industrial coatings

in chemical and mechanical plant, as well as civil structures including bridges.

Points of Contact

Principal Investigator

Dr. Thomas Phely-Bobin

QinetiQ North America

Phone: 781-684-4022

tphely-bobin@foster-miller.com

Program Manager

Weapons Systems and Platforms

SERDP and ESTCP

wp@serdp-estcp.org

Related Documents

Final Report - Limited Distribution Statement B