PTA SCC is a severe corrosion mechanism that particularly threatens equipment made from the common 300-series stainless steels (e.g., Types 304, 316, 321, 347) and their alloys. The cracking occurs when these materials are exposed to , which form from the reaction of:
) mixed with water. A surfactant is frequently added to help the solution penetrate heavy oil or hydrocarbon films covering the sulfide scales.
: Keeping oxygen out entirely to prevent the acid from ever forming. nace sp0170 pdf 2021
): Water introduced through steam-out procedures, ambient condensation, or exposure to air. Oxygen ( O2cap O sub 2
) in the presence of sulfur compounds, iron sulfides form on the surfaces of stainless steel. PTA SCC is a severe corrosion mechanism that
The primary goal is to maintain the mechanical integrity of critical refinery components, such as reactor internals and piping systems, by managing environmental exposure. Mitigation Strategies within NACE SP0170
Oxygen levels must be strictly monitored via continuous testing if any connected lines are broken. 2. Alkaline Washing (Neutralizing Acids) : Keeping oxygen out entirely to prevent the
Implementation of these standards is the responsibility of specialized inspection, operations, and maintenance teams during planned turnarounds.
: When applying alkaline solutions, caution is required around certain catalysts, and adequate rinsing/drying protocols must be observed to avoid subsequent chloride stress corrosion cracking from low-quality wash water. 3. Dry Air Purging (Preventing Liquid Water)