When faced with a decision to choose between PMI or Chemical Analysis to determine the chemistry of a sample, how do both methods stack up against each other? This article will explain the main differences between them and explore the advantages and disadvantages of both.
Positive Material Identification (otherwise known as PMI) is a rapid, non-destructive method of verifying the chemical composition of a metal or alloy. As a highly portable tool, it offers the quickest and most cost-effective solution to determining the chemical composition of a component or batch material. Its applications are wide ranging from being able to quickly identify large batches of finished product to re-certifying materials. Different techniques such as X-Ray fluorescence (XRF) allow a fast identification of the key elements whereas Optical Emission Spectroscopy (OES) can analyse for carbon and lighter elements.
Chemical Analysis is a more time-consuming and complex solution to determining a materials chemical composition. The versatility of chemical analysis means it can be used in a wide variety of industries such as biological, metallurgical, and chemical uses. For example, ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy) involves a trace level analytical technique by introducing a plasma beam to the surface of the material which in turn emits a spectrum of emission lines that characterise each element within the sample.
To choose the right solution, it is important to weigh the pros and cons for each method as highlighted below.
The main advantages and disadvantages of PMI are:
- Fast and non-destructive method
- Perfect for verification and rough identification of a metallic sample
- Robust machines particularly when used in fabrication and factory environments
- Not as accurate as Chemical Analysis techniques
- Not suitable for confirming 100% full chemistry required for strict standard requirements
- Multiple results required to offer same level of confidence in result compared to one chemical analysis test
The main advantages and disadvantages of Chemical Analysis are:
- Highly accurate quantitative results achieved
- Can be used to pick up trace elements down to parts per million (ppm) or less
- Different analytical techniques offer wide range of versatility in different industries
- Highly sensitive equipment requiring use in highly controlled conditions
- Can be an expensive solution depending on the application and volume of tests
- Tests can be time-consuming
In conclusion, both methods offer a unique solution for material identification, depending on the applications and cost considerations.