Herbert DeFriez Consultant

If you have a problem and you can't figure it out, talk to me.
Corrosion Expert Witness
Forensic Engineering
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Herb Defriez

50+ years, in various forms.

  • Consulting in corrosion as a court-tested expert witness.
  • Experimental incident reproduction as a court-tested expert witness.
  • Forensic engineering in most any engineering field not requiring expert witness testimony.
  • Patent development assistance.

For those of you reading this page, let me give you a short tour of my work history. From 1966 through 1973, I worked for others. From 1973 through 2017, I owned a couple of companies that designed and manufactured source emissions test equipment and performed source emission testing. I sold the source testing company in 2008, just before the crash. Last year, I lost the design and manufacturing business because the EPA was put out of business and no one wanted to buy equipment that they did not need. I am now reinventing the specialty consulting that I did over the years as a fun job. I did not do the normal things one would do if one’s only job was consulting since I had a couple of very good companies that were doing just fine. Circumstances have changed so here I am.


On projects where the outcome is not easily determined up front, I present a plan, the expected times and testing costs and schedule stopping points to review progress and costs. At each of these points, the client gets to look at what evidence we have collected, where it fits in the general problem, see if additional testing will resolve uncertain issues and decide whether to resume with the project or stop. This has always worked, I say again, this has always worked. After 30 years, no one has ever asked for their money back.
1. Origin and cause of corrosion failures with possible mitigating measures. I have a California Professional Engineer’s licence in corrosion and have testified in court, having passed the Daubert Challange.

2. I perform experimental incident reproduction. When I have limited experience with a particular failure, I duplicate the failure experimentally and record the processes that mimic that failure. In this way, I simply lay out the steps to failure discovered by experimentation and those steps are now the “cause” – no “expert opinion” needed. Have testified in court in such cases.

3. In forensic engineering, the goal of the investigation is to reach a degree of certainty that is “more likely than not”, as in “the fire was more likely than not artificially set as scorch marks were found on the dash and under the gas tank”. Such cases are usually reserved for insurance issues and general disputes that do not reach the civil legal level – the cost associated with this degree of certainty is substantially less than for a legal case but can none the less be very useful in resolving disputes. As a graduate chemical engineer with many years of diverse experience, my “guess” is usually much better than the most engineers. Additionally, should I discover I really can’t solve the problem, I most likely know a specialist that can.

4. Patent development assistance. As the holder of three patents, I have experience in assembling the concepts and words in such a way as to garner the greatest number of claims about the subject of the patent. Patent attorneys make the patent “legal”, I try to make the patent “useful”.

A Look Inside the world of corrosion

When you must have an answer, you call Herb.
Particularly in corrosion, normal human experiences in no way prepare you for the actual truth of the situation. Flash rusting can make a perfectly safe wall interconnect plate look like it has almost corroded away until you get up close and notice that the corrosion thickness is less than 0.005″, but, that produces a lot of very red iron oxide rust that looks like failure. Stainless steel on the other hand can look perfectly OK, only to observe stress corrosion cracks that produce no rust staining at all but the metal has no structural integrity due to the cracks completely through the plate. I am here to arrange the risks in order of importance, allowing the client to determine a reasonable course of action based on educated, experienced observation. That is my goal.


“My name is Sean Onodera and I work for TerraChem, an oilfield production chemical company. Among many things that my company provides its customers is corrosion mitigation and prevention. Corrosion in my field varies from CO2, H2S, O2, electrolysis and erosion. When asked for a second opinion on some difficult corrosion problems, I turned to Herb for answers and help. Herb’s reports were very detailed and thorough. Not only did he give great reports, we discussed why such problems occur to help me to identify problems and patterns for future failures. I highly recommend Herb for any corrosion problem you have a question on.”
– Sean Onodera


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