3 Tips to Achieving a Quality Appearance for ASTM B633

ASTM B633 is the most common standard for Zinc Plating. Within this standard are six Plating Types determining the chromate, and four Service Conditions defining the plating thickness based on a parts end-use environment.

A complete ASTM B633 specification will identify the requirements for both Type and Service Condition.

Zinc Plating is an industrial finish applied to protect parts from corrosion. It's common to meet corrosion performance standards while experiencing variations in appearance between parts and among different orders.


What do I need to know about the appearance of ASTM B633?

  1.    The Surface Condition of your Part Matters

  • Unlike coatings such as paint, electroplating does not fill in porous surfaces or smooth-out imperfections.
  •  It can have the opposite effect by replicating the existing surface of a part, therefore, enhancing defects such as cracks, pits, or marks, making them more apparent.


           Part Surface Prior to Plating                                           Post-Plating Surface Appearance

    Part Surface Prior to Plating                    Post-Plating Surface Appearance


 2.    Fabrication Quality will Affect the Plating

  • Parts with incomplete welds, seams, burrs, or areas where two pieces are conjoined, are at greater risk for chemical entrapment or plating bleed-out. These features commonly contain crevices that can entrap plating chemicals that seep out over time. 

  • Smooth surfaces increase the likelihood that all solutions will drain from the part during the plating process leaving the finish intact.




  • For the highest quality coating, parts should be free of defects prior to plating.

 3.    Color Variations are Common

  • The primary purpose of electroplating is to protect parts from corrosion and can be attained with a range in appearance from bright to semi-bright to dull. The appearance of the finish can also vary between parts and among different orders.

  •  Secondary processes such as painting or powder coating after plating can help achieve maximum corrosion protection with a uniform appearance.