#232 from R&D Innovator Volume 5, Number 8          August 1996

From Dentistry to Anti-freeze and Paints
by J. A. von Fraunhofer, Ph.D.

Dr. Fraunhofer is director of biomaterials science at the Baltimore College of Dental Surgery, University of Maryland.

I was trained as a chemist and metallurgist and spent five years helping to solve corrosion problems in industry.  However, I became fascinated with the advances in biomedical engineering, and left industry to work in academia.  Much of my research involved learning how screws, plates and a wide variety of materials, inserted in the body by physicians and dentists to treat fractures or diseases, react in a physiological environment.  I found myself becoming especially interested in dental materials because of their almost unique challenges:  high stresses from chewing, highly ionic saliva, requirements for biocompatibility and esthetics, as well as the need for reasonable cost and easily and rapidly processible materials.

In 1992, I was professor in the dental school and a consultant biomedical engineer to the department of Orthopedic Surgery at the University of Louisville.  A colleague there had just accepted a position at another university, and his assistant needed a new supervisor.  While interviewing the assistant, she told me about the project she had been working on, inhibition of bone growth by tobacco.  It turned out that the very small levels of nitrosamines in tobacco seemed to hinder chicken-bone development. 

New Value in Tobacco Juice?

Like most people, I was aware that many plants contained a variety of chemicals, many of which were important or had special properties, but never thought about the matter in any great depth.  However, upon reflection, I began to realize just how complex the plant kingdom could be, and that herbs, tea, coffee and a vast array of medicines and drugs come from plants.  I wondered what kinds of compounds were in tobacco.  From a brief literature search, I learned that tobacco contains more than 2,700 different compounds, with relatively large concentrations of carboxylic acids, polyphenols, terpenes, and amines.  Many of these chemicals can be electrochemically active, so I wondered if they could function as metal corrosion inhibitors. 

When a metal corrodes, positive ions enter solution, leaving a negative charge on the metal surface.  An electroactive compound may attach to the metal and prevent the release of positive ions, may change the charge on the metal, or even form a protective film on the surface, thereby reducing or stopping corrosion.

Corrosion is big business, as it is a major consumer of metals and costs billions of dollars per year in the U.S.A. alone.  All metals have to be protected against corrosion, either through a paint coating that contains a corrosion inhibitor or by adding protective chemicals, as in cooling systems for car engines or cooling or heating systems for buildings.  Chemicals that are routinely used as anti-corrosion inhibitors include chromates, benzoates, nitrites, and phosphates.  Virtually all of these chemicals are toxic or cause environmental pollution problems.  Regulatory agencies are on the lookout for safer alternatives.

Could tobacco somehow be used to control corrosion?  Tobacco is normally considered as a smoking substance, but I thought that obviously some materials can get into the body through water extraction since people (like baseball players) chew wads of tobacco.  So I went to the local cigar store and purchased some chewing tobacco.  Then I stewed it  with water, and filtered out the residue.  The process was like making tea.  Now I wanted to test the juice for its possible anti-corrosion properties.

Protecting Metal

I set up various metal couples, such as steel versus copper, aluminum versus brass, and titanium versus gold.  They were immersed in a one percent salt solution.  I measured the corrosion reaction by using a zero-resistance ammeter (a device that measures current without draining current from the system, and affecting the results) to test the galvanic current.  When I added tobacco extract--eureka!--corrosion was significantly inhibited.  In fact it was far more active as an inhibitor than chromate, which is commonly used as a corrosion inhibitor in industrial settings!

Then I set up a test with steel in a ten percent sulfuric acid solution.  The tobacco extract almost completely stopped metal dissolution!  Remarkable!  This seemed to have potential to be commercially important.  Through the university I applied for a patent, which recently has been granted, on this discovery.

When I evaporated the liquid from tobacco extract, the powder itself exhibited anti-corrosion activity when added to the test solutions.  Initially I thought of its application to dentistry.  Corrosion easily occurs when two different metals are on adjacent teeth; for instance, a gold crown and an amalgam filling, or metals on partial dentures.  These galvanic currents in the mouth can cause discoloration of the metal as well as pain.  I wondered if tobacco extracts could be included in toothpaste to hinder this corrosion.  However, I quickly realized that health concerns about tobacco would most likely not make this a good product for such use. 

Possible Applications

I then wondered whether tobacco extract could be used in industrial settings.  The powder could be incorporated in paint, dispersed in anti-freeze, or added to water-cooling systems.  My calculations had the tobacco powder as costing far less than corrosion inhibitors currently in use.  Besides, the solid material that’s left over after extraction and filtering could be plowed under and used as fertilizer.  I contacted cooling system manufacturers and paint producers, both troubled by corrosion problems.  These industries were very enthusiastic.  They would love to have better, less expensive, and more ecologically compatible, corrosion inhibitors. 

For smoking or chewing tobacco, small twigs and stems have to be removed; but for my process, they caused no problems when used alone or mixed with the leaf material.  This indicated a possible new market for tobacco, so I wrote to and visited several tobacco companies for funds to further develop my finding; however, none seemed to have any interest. 

So what could I do?  When all else fails, do it yourself!  I, and a technology-transfer entrepreneur, recently formed a company, Inhibitex.  We’re pushing ahead with the concept, and are currently developing this "natural" rust inhibitor.  The next chapter in this story is certainly going to be exciting.  And I often think back to the start of this venture, when I was listening about a project I had no direct interest in:  tobacco components that inhibit bone growth.