1. Rinsing Pollution
After quenching the fasteners, use silicate to clean and rinse them. If there were some solid matter on the surface, and found to be iron oxide and inorganic silicate by infrared spectroscopy, this was due to the incompletely rinse and silicate was remained on the fastener surface.
2. Excessive Corrosion
We often see some black stripes on the surface of carbon steel flanges. Though the fasteners have been rinsed by inorganic and organic detergent before heat treatment, there still had black stripes after quenching. Even with carefully cleaning, black stripes were still on the surface. Using infrared spectroscopy to analysis the surface residues and found to be calcium and sulfur with higher concentrations. Then, using a small piece of test filter paper to swab the black spots until the spots left on the filter paper. With infrared spectroscopy analysing the test paper, sulfur, calcium, manganese, iron and chromium were confirmed to be the main elements. Calcium and sulfur, these two elements, indicted that the material is dried quenching oil. Because of the excessive aging of quenching oil, so it was recommend to pour old oil and add new oil, and implemented supervision and maintenance of the entire process.
3. Surface Residues
Use infrared spectroscopy to analysis white residues on the carbon steel flanges. Without acidic cleaning agent, but there was high carbon solubility in the rinsing tank, then you should regularly replace the bath solution.