In contrast to mixed acid pickling systems, which is still in use today, the technology contains no HNO3 (nitric acid), and removes all scale, iron contamination and welding oxides.
Manufacturers face strict health, safety and environmental (HSE) regulations due to the release of potentially harmful substances, such as NOx emissions in the air and nitrate effluents in water.
“At our keg plant at Zaragoza, in Spain, we decided to implement Henkel’s Bonderite C-CP 1300 pickling and passivating process because of its excellent combination of high productivity and uncompromising sustainability,” said José Enrique Gerona, GM, Entinox.
Bonderite C-CP 1300 can be used in spraying or immersion lines and is suitable for most stainless steel grades such as austenite, ferrite, martensite or duplex, including high-chromium AISI/SAE 4XX.
The system includes a starter (ST) for bath make-up, two components (R & Z) to maintain the acidity of the bath and the oxidizing and passivating capacity of the pickling solution, with an optional accelerator (TO) for tough to pickle materials.
Entinox’s kegs come in a 1.4307 (AISI 304L) grade stainless steel sheet, which is one of the most widely used austenitic chromium-nickel steel alloys.
After bending, forming and welding, each keg has a surface of 2 square meters. Prior to pickling, the barrels are cleaned and degreased using a Bonderite C-AK product in a spray washer.
The Bonderite C-CP 1300 R & Z mix is then applied in another spraying step.
Longer bath life
The Zaragoza plant has a production capacity for up to 450,000 barrels per year and offers kegs in sizes of 20L to 50L and 7.75 and 15.5 US gallons, and customized barrels.
“Our Bonderite C-CP 1300 process was developed to eliminate the risks associated with HNO3 in traditional mixed acid pickling systems,” said Ronald Elemans, business development manager, Cleaners, Henkel.
“Nitrogen oxide emissions from these systems can lead to significant neutralization costs, and there is no feasible way of removing nitrate effluents in waste water.
“Both factors also limit the possibility of increasing the productivity of the pickling process without heavy investments for NOx and NO3 ion removal.”
Angel Roche, technical manager, Entinox, added, while the resulting corrosion resistance is on par with that provided by mixed nitric acid-based systems, Bonderite C-CP 1300 has a significantly longer bath life.
“As it is nitric acid-free it eliminates the risk of nitric fumes within the production area. And the absence of hexavalent chromium means all effluents can be treated in our existing waste water plant,” said Roche.