Background

To prevent or inhibit corrosion on ships, bridges, and other marine structures, chromium VI ions have been applied to aluminum surfaces in various chemical compounds.  Strontium chromate, zinc chromate, and chrome phosphate are excellent pigments which have been commonly used.  However, these compounds are carcinogenic and their use is now prohibited.  The chromium ions are easily leached from most paints by simple immersion of the paints in water.  A new pigment was desired which is both effective in corrosion prevention and environmentally acceptable.
 

Objectives

The objective of this project was to find an inhibitor which can prevent corrosion while being environmentally friendly.  A further objective was to incorporate the successful pigment into a practical paint system and thus demonstrate its feasibility.

Application and Potential Uses

Thousands of planes and ships, both military and commercial, need to take advantage of the light weight and strength of aluminum in environments where ordinary aluminum corrodes, such as along seacoasts where salt breaks down the normally protective aluminum oxide forming on the metal.  Similarly, many land vehicles, storage tanks, signs, buildings, and other aluminum structures need protection.

Principal Industry Collaborators

Several aluminum companies have collaborated in this project.  Comaleo of Australia, Alcoa, and Reynolds have all provided aluminum lithium material for research.  Euronavy USA has provided a set of paint vehicles, including latex, epoxy, and solvent based.

Project Status Summary

The researchers have been successful in developing a substitute pigment consisting of an aluminum lithium particle.  It is used at various mesh sizes from 100 to 400 mesh approximately 0.001-inch in diameter. In activating the surface, the pigment was heated to 350 C for 15 minutes under an argon blanket to prevent premature reaction with air.

The researchers created a sample paint with lithium silicate (water glass) that was applied to hand cleaned aluminums of various alloys. The adhesion quality was from good to outstanding.  The flexibility was not tested, but should be very good. When the paint was tested by an independent testing organization to ASTM-B117 (salt fog) for 168 hours on scribed panels, no corrosion occurred.

As part of the ongoing research, many other preliminary products will be developed. Practical development tests, such as application parameters, long term testing, shelf life, and other handling characteristics remain to be determined.

Manufacturing of the water-based system ultimately should be simple, providing the formula is not changed substantially.  The argon treatment is not costly, but it does add another step in the preparation of the paint and necessitates a sealed container.  The ingredients are low to moderate in cost, as well as being environmentally friendly.

Future Plans

As part of a planned two-prong approach, a useable product will be developed from the prior work while other possible variations will be investigated. The concept of this project is to develop not only a new paint, but a new corrosion inhibiting system.
 

For more information contact:

Mr. Alfred F. Daech
Telephone: 504-280-6054
E-Mail: afdce@uno.edu

GCRMTC TECHNICAL BRIEFS are published periodically by the Gulf Coast Region Maritime Technology Center, a U.S. Navy Center of Excellence in Advanced Marine Technology based at the University of New Orleans.  GCRMTC's Mission is to "enhance international competitiveness in the U.S. shipbuilding industry through sponsored research."   For additional information, contact:  GCRMTC, University of New Orleans, New Orleans, LA 70148, Tel: (504) 280-3871, Fax: (504) 280-3898, E-mail: jtsen@uno.edu

The contents of this publication reflect the views of the MERIC staff and are based on information obtained from the literature.  The contents do not necessarily reflect the official views or the policies of MERIC or the Gulf Coast Maritime Technology Center.  This publication does not constitute a standard, specification, or regulation.  MERIC does not endorse products, equipment or manufacturers.  Trademarks or manufacturer's names appear herein only because they are considered essential to the object of this publication.