15 of the Most Common Causes of Failure of Traditional Protective Corrosion Coatings
While these 15 most common causes of failure are based on a traditional model of corrosive management, Rust Grip® and Moist Metal Grip blow things away with their single application proven corrosion protection.
Rust Grip® is a one-coat, patented encapsulation—interior and exterior—surface protection coating that also acts as a full containment covering single component urethane formula applied directly to rust or blasted metal surfaces.
Moist Metal Grip is a two-part (2 component), touch adherent, epoxy coating which produces a hard, yet flexible coating film designed for application on dry, moist, wet or submerged surfaces for protection against corrosion and chemicals.
15 of the Most Common Causes of Failure of Traditional Protective Coatings and the Type of Failure
- Inadequate blasting and insufficient removal of mill scale from the steel leading to poor adhesion
A. Rust Grip® needs a maximum of NACE 3 blasting but can also be cleared with hand tools
2. Use of blasting grit with soluble salt contamination leading to osmotic blistering and under film corrosion
3. Oil contaminated compressed air used for blasting leading to surface contamination leading to poor adhesion and delamination of the coating
4. Inadequate blast profile i.e. shallow valleys leading to poor adhesion
5. Excessive blast profile i.e. high peaks leading to poor steel coverage and risk of rust-rash corrosion, particularly for low DFT coatings.
6. Excessive delay between blasting and coating causing flash corrosion contamination leading to poor adhesion and corrosion cells
7. Addition of too much thinner that increases the potential for porosity and pinholes in the coating. There is also an increased propensity for the formation of Bernard Cells where there are boundaries of resin rich coating, resulting in “crows feet” cracking.
8. Poor mix ratio of the epoxy with the hardener leading to incomplete cure
9. Inadequate mixing/stirring of the coating before application leading to poor distribution of barrier pigments leading to coating cracks and premature corrosion
10. Inadequate coating specification: lack of suitable topcoat for UV sensitive epoxies leading to chalking and UV breakdown
11. Inadequate curing of coatings leading to less than optimal properties of the coating with increased moisture penetration and formation of corrosion cells
12. Incompatibility of coating if different paint systems are used multicoat application leading to delamination/peeling
13. Poor QA leading to inadequate control of coating thickness (e.g. excessive DFT) leading to cracking of the coating due to residual stresses
14. Poor QA leading to inadequate control of coating thickness: low coating thickness or missing coats can lead to poor barrier performance and premature corrosion
15. Exceeding the recoat window leading to delamination of topcoat from primer coat due to blast-dust contamination or lack of interfacial adhesion.
Source: ExcelPlas
