Overview

Cleaning and Passivation are two processes that are inherently linked. Proper passivation of stainless steel components cannot occur if parts are not cleaned of contaminants such as dirt, and especially, oils, prior to beginning the passivation process. For this reason, it was a natural evolution to enhance our immersion processing designs to be compatible, and successful, passivation systems.

ASTM (www.astm.org/) has published, along with SAE (www.sae.org/), definitive and often requested specifications that define nitric passivation typically as “method 1” and citric passivation as “method 2”. This numbering has no bearing on the superiority of one method over the other. Both methods are satisfactory in their ability to passivate stainless steel parts. The question really comes down to what your customers demand, and what your appetite for dealing with nitic acid is. Either way, ACT has engineered modules for passivating stainless steel to compliment its standard and custom cleaning systems.

ACT’s systems currently passivate to    A STM A380   , ASTM A967, and AMS  2700. K ey to our success has been a large investment in R & D and testing of materials to ensure survivability not only in contact with the liquid nitric acid, but also the fumes. Both are hazardous and can quickly cause damage to materials in the vicinity of nitric systems. ACT can assist with the room planning for such systems, but ultimately extensive research into handling the acid (both fresh and spent), the personal protective gear and safety practices required for personnel in the area, and air quality and air movement in the system’s location should be done by the customer. Verification of “the spontaneous formation of the protective passive film” as stated in ASTM A380 can be achieved using  a variety of methods in the specification, but the copper sulfate test is most common for both nitric and citric passivated parts.

Citric passivation has been effectively used for many years but only with its acceptance in the SAE  published AMS 2700, superseding previous methods in aerospace passivation, has more industry acceptance been observed. It seems many old school factories refuted the scientific data which indicated, by salt spray testing, that citric passivation can not only be an equal, but better passivation method for aerospace parts. ACT is a distributor of the Citrisurf products manufactured by Stellar Solutions out of Illinois (http://www.stellarsolutions.net/). Mr. Kremer at Stellar has been one man army, crossing the globe incessantly, spreading the virtues of citric passivation and his products are successfully deployed in many ACT systems. Unlike nitric passivation, the foodgrade Citrisurf products are completely safe for the parts, operators, and the environment for the parts from many industries.

Contact ACT to discuss your project requirements. Reaching out to ACT will surely result in a quick understanding of each process as they pertain to our systems, and what we can do to help your company gain process consistency and profitability with passivation.