Neutral Aqueous Cleaning Solution for Rouging Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The removal of rouging, a type of surface change characterized by iron oxide or iron hydroxide deposits on stainless steel surfaces in pharmaceutical and food processing industries, is challenging due to the need for harsh chemicals like mineral acids, which pose safety risks and are inefficient, especially in systems using ultrapure water or vapor.
Innovation Solution
A neutral aqueous cleaning solution containing a reducing agent, such as dithionite, combined with complexing agents like diacetic acid compounds, is used to effectively remove rouging deposits at neutral pH, preventing contamination and safely restoring the chromium oxide passive layer on stainless steel surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mineral acids are used to remove rouging deposits, then the removal effectiveness is improved, but safety risks and environmental harm increase
Solution Approach 1:
The patent changes the chemical parameters of the cleaning solution from acidic to neutral pH, and from oxidizing to reducing environment. Specifically, it uses reducing agents like sodium dithionite or sodium hydrosulfite in neutral aqueous solutions to convert insoluble Fe(III) oxide deposits into soluble Fe(II) complexes, achieving effective rouging removal without the harmful effects of mineral acids
Solution Approach 2:
The patent converts the harmful effect of iron oxide deposits (which are difficult to remove) into a beneficial process by using reducing agents that transform the insoluble Fe(III) oxide into soluble Fe(II) species. This chemical transformation turns the persistent contaminant into a removable form, achieving cleaning effectiveness without acid corrosion
2Productivity
If traditional acid-based cleaning methods are used, then rouging deposits can be removed, but damage to stainless steel surfaces occurs
Solution Approach 1:
The patent fundamentally changes the pH parameter from acidic to neutral, and the redox state from oxidizing to reducing. The neutral reducing environment selectively dissolves iron oxide deposits through reduction to Fe(II) while preserving the chromium oxide passive layer that protects stainless steel, thus removing deposits without damaging the metal surface
Solution Approach 2:
The patent introduces reducing agents (sodium dithionite or sodium hydrosulfite) as intermediary substances that mediate the removal process. These agents selectively react with iron oxide deposits to form soluble complexes, acting as intermediaries that facilitate deposit removal without directly attacking the stainless steel substrate
3Productivity
If harsh chemicals are used for cleaning, then cleaning effectiveness is improved, but contamination risk increases
Solution Approach 1:
The patent changes the chemical nature of the cleaning solution from harsh acids to mild neutral reducing agents. This parameter change enables effective cleaning while minimizing contamination risk, as the neutral reducing environment does not introduce harmful residues or cause cross-contamination in pharmaceutical and food processing systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for the complete and safe removal of rouging deposits without damaging the stainless steel surfaces, reducing the risk of contamination and improving the operational life of equipment, while being safer and more environmentally friendly than traditional acid-based methods.
Implementation Method 1
The invention uses reducing agents, in particular dithionite and/or disulfite, to convert the multivalent insoluble oxidic metals present in the surface changes to more soluble forms such as iron(II)
Implementation Method 2
The complexing agents prevent the formation of crusts by complexing the iron(II) ions
Data Source
AI summary
The invention relates to a method for removing films and deposits from stainless surfaces, especially from stainless metallic surfaces such as they are used in process stations and production units in the pharmaceutical, food and biotechnological industries, and to an aqueous cleaning solution comprising a reducing agent, in particular dithionite and/or disulfite, and at least two different complexing agents, wherein one of these complexing agents is a compound comprising diacetic acid groups or a salt thereof, for removing rouging on surfaces of stainless steels that come into contact with media selected from the group of chromium/nickel and chromium/nickel/molybdenum steels in the neutral pH range.