Analytical Chemistry
Analytical chemistry is critical to the materials and corrosion sciences. It allows us to understand the material that we are testing, or helps us understand the environment that might be degrading the material in question. We use analytical chemistry in a variety of applications in the laboratory, either inclusive in an investigation or test program, or characterization of your samples.
CTL utilizes a variety of analytical chemistry techniques during testing and investigations. These methods help us characterize materials, solutions, and deposits. We frequently employ these techniques to evaluate corrosivity of water, soil, and deposits. This helps to indicate environmental corrodents that can be driving problems or identify unknown component composition.
CTL offers these services inclusive in evaluations, but also as individual services for individual sample analysis. For per sample costs please see CTL’s pricing handbook.
Most materials absorb IR energy at different wavelengths depending upon their chemical nature. This phenomenon provides a method for characterizing many materials. IR energy is passed through the sample and the absorbance and/or transmittance versus IR wavelength is measured. Output is in the form of a graph, which is called the IR spectrum. The spectrum is a “fingerprint” of the material. It can be compared to those of known materials (reference spectra) to identify the unknown material.
The spectra of long-chain hydrocarbons (mineral oils, waxes, polyethylene) will be very different from the spectra of esters (vegetable oils, synthetic oils, acrylates), making different class groups easy to identify. To characterize materials within a class group more subtle differences in the spectra can be used to narrow the identity of the substance (Spectral Interpretation). For very closely related materials like vegetable oils (corn, cotton, linseed) the method can only characterize the material as a vegetable oil, but not identify individual oils.
If spectra of two materials are the same with respect to both IR band position (wavelength) and relative band intensity, then the substances are considered chemically similar or closely related. A number of specifications (Mil-Spec, USP, ASTM) use the IR method for material identification.
Ion chromatography (IC) can be used for analysis of anions in an aqueous solution. For example, IC analysis of water samples or extractions of soluble species from deposits/insulation/soil are common. These anions are often implicated in corrosion problems.
Anions we commonly analyze for include:
- Fluoride
- Chloride
- Phosphate
- Nitrite
- Nitrate
- Sulfate
- Acetate
- Formate
Wet chemistry is a form of analysis that uses Photometric (Hach) or Titration Procedures. This includes acidity, alkalinity, hardness, chlorine, triazoles, and other analytes. These methods are used to generate information for water and soil analyses.
Sample preparation may include one of several extraction methods to obtain an aqueous solution for analysis from a solid or solid surface.
Scanning electron microscopes have been commercially available since the late 1960’s. The instrument has evolved from a highly specialized research laboratory instrument into an accepted part of analytical laboratories and production facilities. With the capacity of magnifying features from 10 to 100,000X, it can be found in the businesses of semiconductor and nylon fiber quality assurance, pollution particle characterization, and equipment failure analysis. The SEM also serves as a platform for micro-analytical techniques, such as Energy Dispersive X-ray Spectroscopy (EDS). In combination with this technique, the SEM becomes a powerful tool for ferreting out and characterizing evidence for root cause failure analysis. Both mechanical and corrosion related failures often have features that can be best discerned at high magnification and identified by x-ray microanalysis.
One of the instruments most commonly used in conjunction with the SEM is the Energy Dispersive X-ray Spectrometer (EDS). The x-ray spectrometer converts an x-ray photon into an electrical pulse with specific characteristics of amplitude and width. A multi-channel analyzer measures the pulse and increments a corresponding “energy slot” in a monitor display. The location of the slot is proportional to the energy of the x-ray photon entering the detector. The display is a histogram of the x-ray energy received by the detector, with individual “peaks,” the heights of which are proportional to the amount of a particular element in the specimen being analyzed.
Soils are analyzed for corrosivity using the Critical Parameters and Rank Numbers for Soil Aggressiveness, from the“Handbook of Cathodic Protection, The Theory and Practice of Electrochemical Corrosion Protection Techniques” by Von Baeckmann and Schwenk. The paramaters that can be analyzed in the laboratory are listed below.
- Kind of Soil
- Specific Soil Resistance
- Water Content
- pH
- Total Acidity to pH = 7
- Redox Potential
- Total Alkalinity to pH = 4.8
- Sulfide
- Chloride
- Sulfate
Water quality is critical to prevent pitting, corrosion, and scaling in systems. For example, poor water quality can cause pitting corrosion in domestic water systems. As many home owner knows, hard waters can cause excessive scaling. In HVAC, quality is crucial to system longevity. Preventative testing can help detect concerns before they become costly failures, or help identify critical parameters for remediation and future monitoring after issues occur.
CTL commonly analyzes water samples for the purposes of determining the corrosivity including the following:
- pH
- Anions (chloride, sulfate)
- Hardness
- Alkalinity
- Total Dissolved Solids (TDS)
- Conductivity
Quantitative polymerase chain reaction (qPCR) testing is a type of DNA testing. It identifies the functional genes related to bacteria species of interest to help quantify their presence. CTL uses this information most commonly with investigations related to microbiologically influenced corrosion (MIC). Our current qPCR testing can target the following: SRB (Sulfate-reducing bacteria), IRB (Iron-reducing bacteria), and Total Bacteria. Other species, including total archaea, sulfate-reducing archaea, acid-producing bacteria (acetic and butyric acid producers), denitrifying bacteria, and methanogens, can be identified using a subcontractor.