What is the impact of medium solid particles on the corrosion rate of 316 stainless steel heating tubes?

# What is the influence of medium solid particles on the corrosion rate of 316 stainless steel heating tubes? Residual mycelium, protein precipitates, and inorganic solid particles are frequently present in fermentation culture media that are produced during the metabolism of the strain. These suspended solids continuously scour and abrade the surface of 316 stainless steel heating tubes in circulating pipelines, resulting in the complete destruction of the chromium-rich passive film and a significant acceleration of pitting corrosion. The premature leakage of heating tube welds within one year of operation is a consequence of the fact that many workshops only monitor chloride and alkali temperature indicators, disregarding solid particle erosion. The correlation between corrosion acceleration degree and particle content is quantified in the subsequent table. | Mass Concentration of Solid Particles | Main Abrasion Location | Passive Film Damage Level | Corrosion Rate Growth Multiple | Recommended Control Strategy | | ---- | ---- | ---- | ---- | ---- | | Less than 0.1 g/L | Minor abrasion on smooth tube body | Slight uniform thinning of film | 1.2 times the standard rate | Weekly simple pipeline flushing | | 0.1–0.5 g/L | Obvious wear at elbow and weld joints | Local film peeling, micro-exposed metal | 2–3 times the standard rate | Install 100-mesh front filter for medium circulation | | 0.5–1.0 g/L | Deep abrasion grooves on heating sections | Continuous film loss at fixed positions | 4–6 times the standard rate | Bi-weekly ultrasonic wall thickness scanning | | Over 1.0 g/L | Severe groove-shaped abrasion on welds | Large exposed metal area without protection | 8–10 times the standard rate | Increase two-stage filtration and shorten overhaul cycle | The chromium oxide passive film of 316 stainless steel is only several microns thick, with soft texture and weak anti-abrasion performance. The protective film on the tube wall is perpetually scraped off by mechanical friction when solid particles flow with the medium at high speed. Pipeline elbows and weld junctions are the first locations where the passive film completely detaches due to fluid turbulence, as they are subjected to the maximum particle impact. Upon the exposure of fresh bare metal, chloride ions in the medium immediately cluster to form electrochemical corrosion cells, and pitting pits expand rapidly under high-temperature heating conditions. The combined damage of chemical corrosion and mechanical abrasion is significantly more detrimental than a single instance of chloride erosion. The standard chloride threshold of 50 ppm allows for the stable operation of 316 stainless steel for a period of 2 to 3 years without interference from solid particles. The corrosion rate will increase, and hidden pitting will appear on welds within half a year if the solid particle concentration exceeds 0.5 g/L, despite the strict control of chloride below 40 ppm. As a result of the decomposition of residual organic compounds that are affixed to abrasion grooves, acidic substances will be produced, which will exacerbate local corrosion and create internal pits that are difficult to detect. The most direct method of reducing solid particle erosion is to use front-end filtration equipment. The majority of mycelium and precipitation can be intercepted by installing multi-layer mesh filtration at the inlet of the heating loop.