What is the difference between pre-coating passivation and pickling passivation?
Thread Content
Hello everyone, what is the difference between pre-coating passivation and pickling passivation? Is the medication different? Is the achieved effect the same?
The method of using an acid solution to remove scale and rust from the surface of steel is called pickling. It is a method for cleaning metal surfaces. It is usually carried out together with pre-passivating treatment. Acids used for pickling include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, chromic acid, hydrofluoric acid, and mixed acids. The most commonly used ones are sulfuric acid and hydrochloric acid. Due to the strong corrosive effect of acids on metals, corrosion inhibitors need to be added. After cleaning, the metal surface turns silver-white; at the same time, the surface is passivated, enhancing the corrosion resistance of stainless steel. Passivation is a method of converting the metal surface into a state that is less susceptible to oxidation, thereby slowing down the rate of metal corrosion. Additionally, the phenomenon in which the chemical reactivity of an active metal or alloy **decreases**, resulting in a noble-metal-like state, is also called passivation. The passivation of metals can also be a spontaneous process (such as the formation of an insoluble compound, namely an oxide film, on the metal surface). In industry, passivators (mainly oxidizing agents) are used to passivate metals, forming a protective layer. Common examples: Cold concentrated sulfuric acid and cold concentrated nitric acid can cause passivation in both iron and aluminum.
I have a question: is there any difference between pre-coating passivation and pickling passivation? Can it be understood that acid pickling passivation is a type of pre-coating passivation?
Hello, I’m about to start working on the plans for this project. I talked with the supplier the day before yesterday; after applying the pre-coating and passivation treatment, the entire system will need to be reprocessed again after 2-3 years, as this treatment only serves to delay pipe corrosion. If you use acid washing and passivation, will it need to be done again after 2-3 years? Or does it take longer than expected for the passivation to occur?