Advantages of Hard plated standards
- Typically hard plated standards are easier to produce and therefore are significantly lower in price
- Hard plated standards are much more robust than foil standards and therefore have a significantly longer lifetime than foils. Foils are inherently fragile and can be easily damaged if not handled properly. Foils may even develop spontaneous defects due to surface tension or stress inherent to the coating. Environmental factors may also be responsible for apparent spontaneous damage to a foil standard.
- In a few cases, hard plated standards exhibit better thickness uniformity than foil standards.
- Hard plated standards do not need protective films. Most foil standards either have a thin polymer film as a support matrix, or they are coated with thin polymer films for added support and protection. These organic films generally do not affect XRF measurements because they are organic in nature and relatively thin, so that their relative x-ray absorption properties are very low. However, in some cases, these protective or supportive organic films can contribute some error to XRF measurements. This is especially true when measuring low energy x-ray lines (< 4 KeV), where the absorption properties of the organic films used to protect and/or support foils can become significant. These films also limit the practical number for combining foils to 3 foils maximum. Adding more foil standards together to create a new combination standard may cause measurement errors due to the combined effects of the multiple organic layers which will exist when multiple foils are added together.
- Hard plated standards normally have smoother, better appearing surfaces than foils. In some cases the surface appearance of foils and hard standards is similar but in other cases, the surface appearance of plated standards is superior to foils. This is especially true for certain foils which are difficult to make so that they appear smooth and wrinkle free. Good examples of foils which cannot be made to have good surface appearance include Cr, Zn, Rh, Cd and Cu. Although surface appearance does not affect XRF calibration and measurement accuracy, many customers prefer standards with good surface appearance.
- Hard plated standards often have better thickness uniformity than foils. In some cases, due to the nature of the process used and the nature of the material, the foil thickness uniformity cannot meet our normal specifications. Using smaller x-ray beams reveal inconsistencies in thickness from the center of the standard to small distances off-center. This is especially true for certain foil materials which can only be made using mechanical processes. Some examples include specific thickness ranges of Zn, Cu, Rh, Pt, Ti and Cd. While we continue to work on improved methods of foil manufacturing, hard, plated standards will continue to have better thickness uniformity until the time comes we can implement a process improvement for each case where uniformity of foil thickness is below our normal 5% requirement.