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"CitriSurf® is a perfect and environmentally friendly alternative to passivating with nitric acid!"

Dieter Fuchs, Boehringer Ingelheim Pharma GmbH & Co. KG

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