Steel Advisor

Primers for Steel: Their Purpose and Performance

This article addresses some problems that can occur when primers are incorrectly specified, and examines some misconceptions on their expected performance.

6 December 2020

This article addresses some problems that can occur when primers are incorrectly specified, and examines some misconceptions on their expected performance. Costly remedial rework can be incurred if a shop primer is damaged or exposed to exterior weather conditions for longer periods of time, or that are more severe than were expected, prior to being closed in or subsequent finishing coats being applied on site. These thoughts and observations are based on the author’s experience in the coatings industry. A common cause for arbitration on disputes over coating failures is where a short term, single pack primer has been specified and applied over St 2 (Hand Tool Clean) or more frequently St 3 (Power Tool Clean) prepared steel and left exposed for long periods during construction. Premature breakdown of the coating often initiates from undercut mill scale, transit damage, strop, chain and handling damage if it is left exposed to the weather without repair.

CTG1005.pdf

Michael Williams