CitriSurf®: a superior method
The CitriSurf® method for passivating stainless-steel products is based on a relatively new technology. By means of harmless and environmentally friendly citric acid, the free iron is removed from the surface of any type of stainless steel. The remaining chromium forms a passive layer with the oxygen in the air that is much superior to the natural passive layer with regard to both thickness and durability.
The surface of all stainless steels can be effectively protected against corrosion by appropriate pre-cleaning followed by this passivation. Citric acid is more effective for this than the traditionally used toxic mineral acids, such as nitric acid.
Furthermore, citric acid is much less harmful to the environment than nitric acid or other mineral acids.
In order to achieve maximum corrosion protection, careful pre-cleaning and passivation are indispensable, as only passivated surfaces meet all the requirements (e.g. ASTM 967) and pass all tests, such as the salt-spray test and other validated methods.
In order to optimally prepare the surface for passivation by means of CitriSurf®, alkaline pre-cleaning is helpful, and necessary in particular for stainless-steel types with a high sulphur or carbon content.
CitriSurf® products conform to the current state of technology for effective stainless-steel passivation. Old requirements demanding the use of nitric acid originate from a time when we did not know as much as we know today about the methods and function of the passivation.