After our last blog entry, your boy Blue got quite a few messages, asking bout surface preparation prior to metallizing. So, sit back, relax and let me drop some Steelcoat Family knowledge!
Surface Preparation Prior to Metallizing
Proper surface preparation is the indispensable first step in the metallizing process. Surface preparation includes cleaning the steel (removing dirt, rust, mill-scale, etc.) and roughening the steel surface t create the surface profile or anchor tooth pattern to which the sprayed-metal adheres.
The blast cleaning abrasive (grit) shall be of size and grade that will produce a uniform angular surface profile depth of 2.5 to 5 mils. In general, one can say that the rougher the surface, the higher the strength bond. The
following is taken from an early version of the SSPC-CS 23.00, the precursor of the current Joint Standard on metallizing.
“The depth of surface profile required depends upon thermal sprayed coating thickness. When specifying greater than 12 mils (300 microns) of thickness, a minimum of 3 mils (75 microns) surface profile (not to exceed 1/3 total coating thickness) shall be achieved to ensure coating adhesion. NOTE: Adhesive strength tends to increase with surface roughness”.
The standard for surface cleaning is a “white metal finish” which is defined by both SSPC-SP 5 and NACE no. 1. These specifications are well known and widely available.
Unique to the application of sprayed-metal coatings is the requirement for a specific surface profile which is spelled out in AWS C2.23, NACE 12, SSPC CS-23 otherwise known as the Joint Standard on the application of metallized zinc & aluminum coatings.
“Unless otherwise specified, the steel substrate shall have, at a minimum, a sharp angular profile with a minimum depth of 65 µm (2.5 mils) and a maximum depth of 125 µm (5.0 mils) …”
I would like to thank Joe Butler for helping Olé Blue with some of the technical descriptions & sources! Thank you, Joe! For more information on this subject, please go to www.regalindustrial.com or contact us at 844-855-COAT!