Passivation of Stainless Steel
Passivation is a key part of the pickle and passivation process, which restores the chromium oxide layer, restoring the corrosion resistant properties of stainless steel.
At ICS, we offer a range of chemical pickle and passivation services and products for stainless steel. Our pickle and passivation bath is the largest in Western Australia, using a unique system that pickles and passivates your stainless steel in full compliance.
Pickling, cleans the surface of metals removing oxide layers utilising hydrofluoric and nitric acid. Passivation then accelerates the formation of the oxide layer making it ‘passive’ to corrosion. It is a much less aggressive process utilising different acids such as citric and nitric acid. Passivation does not change the properties of the metal nor will it typically go below the surface unlike pickling.
What is Passivation?
Stainless steel is known and utilised for its corrosion resistance even in environments in which other materials would corrode. The corrosion resistance of stainless steel is due to a thin, chromium-rich complex, oxide film found on the surface of the steel, referred to as the ‘passive layer’. It renders the surface electrochemically passive even in corrosive environments.
Passivation is the process by which a stainless steel will spontaneously form a chemically inactive surface when exposed to air or other oxygen-containing environments (ASTM A380). Even when the surface is damaged such as a scratching or machining, stainless steel will self-repair its anti-corrosion protection layer.
In some cases, exposure to certain environments which deprive the steel of oxygen can prevent the passive layer reforming, such as tight corners, mechanical joints and where welds are incomplete. Degradation of corrosion resistance can also occur during fabrication if austenitic stainless steels are exposed to high temperature ranges. If exposed to these temperatures for too long, areas near the metal grain boundaries can lose their corrosion resistance. This weakness caused by exposure is referred to as ‘sensitisation’. Damage to the passive layer can destroy the self-passivating properties of stainless steel.
This also explains why stainless steel must be kept clean and free from carbon or iron residue in particular. ICS can also provide onsite maintenance services and testing of iron contamination.
Stainless Steel Passivation at ICS
At International Corrosion Services we have developed a system where stainless steels are instantaneously passivated in the pickling bath using Nitric Acid. We also offer onsite pickle and passivation services to prevent corrosion and maintain assets which are immobile.
Through our many years of experience, International Corrosion Services have found that the optimal method to both descale and remove the heat affected zones is a concentration of hydrofluoric acid. We utilise a unique system with a nitric or similar oxidizer, which is then used to passivate the steel and reforms the chromium layer – restoring the corrosion resistance. Although stainless steel does self passivate after 24 to 48 hours, the passive layer is instantaneously formed in the bath blend.Our processes also utilise Avesta FinishOne Passivator 630 for increased protection.
Our standard operating procedures at ICS are delivered working to the ASTM A380, ASTM 967, AS 1627.1 and A 1627.5 standards. The American Society for Testing and Materials have published the main international standards for pickling and passivation including A967 – Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts. The standard covers the different types of chemical passivation treatments with recommendations, pre-cautions and testing methods to confirm effectiveness of treatments.
At ICS, we are equipped to treat almost any stainless steel item. The dimensions of the Pickle & Passivation Bath are:
Pickle & Passivation Bath Dimensions – 13m x 1.45m x 1.2m
Long spools and other items exceeding the bath dimensions can easily be ‘double dipped’ to still achieve a full-immersion treatment.
Alternatively, stainless steel treatments are not only limited to the bath. At our workshop we have a large bunded space for items which are too large, such as tanks, that can be sprayed or brushed to achieve a full pickle and passivation treated to the American and Australian standards.
Where items are immobile, our team can also provide onsite pickling and passivation services. For more information about how we can set up onsite pickling and passivation fill out an enquiry form here.
Avesta 630 FinishOne Passivator
At ICS, we also use the Avesta 630 as a final rinse chemical as part of our standard bath, spray and onsite services. Avesta have shown that the FinishOne Passivator exceeds the performance of nitric and citric acid for cleaning and passivating.
It is a non-hazardous and environmentally friendly chemical to accelerate passivation and remove free iron and other contaminants.
The Avesta 630 is available for purchase in 5L, 10L and 25L bottles. Contact our team today for a quote or read more about the Avesta 630 FinishOne Passivator here.
Key Benefits of our Pickle & Passivation Services
Combined, the pickling and passivation processes removes impurities left through manufacturing, protect the material from pollutants causing corrosion including rust and structural damage, leave the surface smooth and without imperfection and increase the durability and life of the asset.
Benefits of Our Passivation Technique:
– Increased corrosion resistance
– Removal of surface contamination
– Removal of heat tint left after welding
– Removal of rust contamination
Features of our
Pickle and Passivation bath
Pickle and Passivation bath
• Mixer for circulation of the pickling bath.
• Temperature sensor.
• Electrical heaters.
• Electrical control panel and control units.
• Bath cover/lid (manual handling).
• Fumes exhaust system.
• Chemical filtration.
• Waste Disposal and recycling system.
• 10 tonne and 5 tonne overhead cranes.
AFTER TREATMENT YOUR STAINLESS STEEL IS RETURNED TO YOU WITH A CERTIFICATE OF CONFORMITY.
“Example of non-treated stainless steel 18 months after installation”