United States


ACO, Inc. Metal Finishing Department

stainless steel finishing

ACO’s high standards for hygiene in the US require the most hygienic process for manufacturing and finishing stainless steel. ACO operates its facility within the highest standards required by the market within the manufacturing, automotive and aerospace industries. ACO USA has built a state of the art metal finishing shop in its Casa Grande factory in Arizona to support its stainless steel manufacturing plant. The company now offers these processes to third party customers; the most corrosion resistant, hygienic, aesthetically pleasing finishing solution.


ACO Metal Services Include:

  • Electropolishing
  • Degreasing
  • Passivation
  • Pickling


Electropolishing not only passivates the surface but also deburrs, polishes, and removes material (typically .00005” per 10 seconds of run time). Electropolishing is an electrochemical finishing process that removes a thin layer of material from a metal part, typically stainless steel, or similar alloys. This reduces the surface roughness by leveling micro-peaks and valleys which improves the surface finish. The process leaves a shiny, smooth, ultraclean surface finish. Electropolishing is performed by creating an electrolytic cell involving a stainless steel object immersed in an acidic bath. This removes inconsistencies and contaminants on the metal’s surface ion by ion—leaving a smooth, shiny surface when the process is complete.



The Chromium in stainless steel produces a thin layer of oxide on the surface of the steel, the “passive” layer, that prevents surface corrosion. Passivation is essential in the manufacturing process and ensures the quality of stainless steel. A tank of Nitric base solution is used to remove the free iron from the surface of the steel and leaves it in the passive state. Using Nitric acid alone will only be effective on stainless steel and will not work for mild steel. Since stainless already has the ability to “heal itself” the passivation process is used to help it along. Unlike the pickling process there is no material being removed from the base material.



Pickling ensures the imperfections of welding, forming, and machining are removed. Removes a layer of oxides through etching the surface. Removing the thin oxides layer prior to passivation is key to ensure the material receives passivation on every surface. The passivation process will not penetrate the oxide layer if the material is not pickled prior to submersion. Pickling solution consists of Nitric and Hydrofluoric acids. The material is passivated through the pickling process concurrently.


ACO, Inc. Metal Finishing Department

Apart from manufacturing its own product line from stainless steel, cast iron, black steel, polymer concrete, and plastics, ACO is a significant producer for third party finishing services for stainless and black steel. For more information please contact Benito Banda in the ACO, Inc. Metal Finishing Department toll free at  520-210-2611.


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