Comparison between CitriSurf® and nitric acid

According to the standards ASTM A-967 and AMS 2700, stainless steels have to be passivated. This passivation of the stainless steel can be carried out using two methods.

	Nitric acid	CitriSurf®
Safety	Very hazardous	No potential hazards
Air/emissions	Toxic fumes are formed	No toxic fumes
Application	Many safety regulations	Easy application
Passivation	Excellent for many types of stainless steel	Excellent for all types of stainless steel
Environment	Environmentally harmful	Environmentally compatible
Costs	Low procurement costs; high maintenance and disposal costs	Lower total costs on account of longer service life, lower concentration and lower disposal costs
Time requirements	20 minutes to several hours	5–20 minutes, depending on temperature and steel type
Temperature	With some steel types high temperatures are necessary – nitric acid is very dangerous at elevated temperatures	Room temperature satisfactory for many grades, elevated temperature safely improves speed and performance The handling risk does not increase at elevated temperatures. However, the duration of the application can be shortened
Maintenance	Regular disposal as hazardous waste – special protective clothing is necessary	The solution lasts longer and can be disposed of as normal waste, without the need for special protective measures
Removal of iron and iron oxide	Slow removal of free iron	Rapid and thorough removal of free iron and iron oxide
Equipment	Corrosion and damage to equipment is likely	No corrosion to equipment, no special tanks necessary
Flexibility	Time, temperature and concentration have to be closely monitored. With some steel types NOX gasses form	No risks for user, equipment or product in the event of excessively long application or high concentration. No toxic or hazardous gasses are formed
ASTM A-967 AMS 2700	Conforms Conforms	Conforms Conforms