Mechanical Polishing ID/ OD and Passivation (HPT-500/ HPT-500A)

What is mechanical polishing?

Mechanical polishing is used to provide a homogenous and bright appearance. It is accomplished by grinding the tubing with finer and finer abrasive grits to achieve the desired finish or surface roughness. Tubing can be provided in a variety of surface finishes on the Outside and Inside Diameter based on customer requirements.

For ornamental purposes, the outside can be provided in mill finish, bright finish, 180 grit polish, 240 grit polish, 400 grit polish, and even finer depending on customer requirements. For sanitary tubing, the outside and inside are polished to provide a smooth finish to avoid biological buildup on the tubing service. Mechanical polishing can also be used to prepare tubing for electropolishing so that the final desired surface finish is successfully achieved.

HPT-500A specification to which mechanical polishing is done such as ASME BPE A270, ASTM B912, SF1 or any approved variance which applies to specific requirements.

Mechanical polishing is performed to remove contaminants such as:

  • Dirt & Dust
  • Weld Slag
  • Paint
  • Loose Scale
What can be mechanically polished?

HPT can work with you to evaluate your project and determine which finish number would need to be achieved, whether it be #3, #4, #8, 2B, or BA type finish which corelates to the surface roughness(Ra). All material will be polished using industry standards, inspected by trained personnel, and packaged in our class 10,000 cleanroom on site at HPT.

Components, Parts & Systems that can be polished include:

  • Tube, Pipe, Spools, Manifolds, and Fittings
  • Heat Exchangers
  • Valves
  • Fabricated Specials
  • Copper, Carbon, and Stainless Steel
What is passivation?

Passivation is the treatment of the stainless steel with an oxidizing chemical (typically nitric or citric acid) which promotes a thin oxidizing layer to form on the surface of the metal. This thin layer will help protect the metal from chemical attack.

Fabrication of the metal can reduce the overall corrosion performance of the stainless steel; therefore, making the passivation process an essential step. If iron particles become embedded in the surface of the metal during processing they must be removed. If they are not removed, these microscopic particles may promote discoloration, rusting or even pitting. By dissolving these particles in an oxidizing bath, it will enhance the corrosion resistance of the stainless steel thus fortifying the surface of the metal against such attacks.

The passivation process should be the last step in the fabrication process. It is generally performed by immersing the parts in either a nitric acid or citric acid bath and then rinsing in a clear de-ionized water and then dried. If due to the size of the part it is impractical to immerse the part in a bath, the acid solution may be applied to part using a swab and rinsed with water and dried. It is important that the surface of the steel is free from scale, oils or other lubricants prior to the chemical treatment in order for the passivation to be effective.

What can be passivated?

HPT can work with you to evaluate your project and determine which parts and pieces should be passivated. All material will be cleaned using industry ASTM standards, inspected by trained personnel, and packaged in our class 10,000 cleanroom on site at HPT.

Components, Parts & Systems that can be cleaned include:

  • Tube, Pipe, Spools, manifolds, and Fittings
  • Heat Exchangers
  • Valves
  • Fabricated specials
  • Copper, Carbon, and Stainless Steel

All material mechanically polished and/ or passivated receives a certification of conformance after processing. All components, parts & systems will be mechanically polished/ passivated to HPT-500/ HPT-500A specification, inspected, bagged, labeled, and certified.

HPT can also perform mechanical polishing/ passivation with expedited lead times to prevent downtime in your system or project.

Contact HPT today to learn more about our mechanical polishing / passivation services or request more information on our mechanical polishing/ passivation processes.