THE CITRIC ACID PROCESS: CITRIC ACID PASSIVATION
Citric acid is an organic acid unlike nitric acid, which is a mineral acid. It reacts with the iron much better than nitric acid and does not attack the elements in stainless steel alloy, which nitric acid does. And citric acid, overall, is a less harmful chemical than nitric acid. Nitric acid raises problems with environmental disposal, health and safety.
Citric acid, on the other hand, is derived from oranges, utilized in food and beverage products, is acceptable in some instances to go right to the drain depending upon contaminants and local environmental regulations, and is much friendlier when it comes to worker health and safety.
Even the citric acid process itself, passivation, is easier. Stainless steel must be cleaned prior to any passivation procedure. All surfaces contaminated with oil, grease, chips, grinding dust, lapping compound, buffing compound, coolant, and/or swarf must be removed.
Above are three different citric acid passivation systems designed and built by Ramco. The lines were developed based on the batch load size and weight, cleanliness level of the parts prior to passivation, and the required throughput per hour.