Corrosion Fatigue Behavior of Twin Wire Arc Sprayed and Machine Hammer Peened ZnAl4 Coatings on S355 J2C + C Substrate

Abstract

Offshore installations, e.g., offshore wind turbines and pipelines, are exposed to various mechanical loads due to wind or waves and corrosive loads such as seawater or mist. ZnAlbased thermal sprayed coatings, often in conjunction with organic coatings, provide sufficient corrosion protection and are well established for applications in marine environments. In this study, machine hammer peening (MHP) is applied after twin wire arc spraying to improve corrosion fatigue behavior through increased hardness, reduced porosity, and roughness compared to as-sprayed coatings. Mn-alloyed structural steel S355 J2 + C with and without ZnAl4 coating as well as with MHP posttreated ZnAl4 coating were cyclically loaded in 3.5% NaCl solution. MHP leads to a uniform coating thickness with lower porosity and roughness. ZnAl4 coating and MHP post-treatment improved corrosion fatigue behavior in the high cycle fatigue regime with an increase of the stress amplitude, applied to reach a number of cycles 1.2 × 106, up to 115% compared to sandblasted specimens. Corrosive attack of the substrate steel was successfully avoided by using the coating systems. Stress- and microstructure-dependent corrosion fatigue damage mechanisms were evaluated by mechanical and electrochemical measurement techniques.

Effect of the Surface Chemical Composition on the Corrosion Resistance in the Mixture of FeCrMoNbB (140MXC) and FeCMnSi (530AS) Coatings Produced with the Electric Wire Arc Spraying Technique: Part I

“…COTECMAR (Science and Technology Corporation for the Development of the Naval Maritime and Fluvial Industry), as an institution representing the Colombian naval industry, installed TWAS equipment (SYSTEM EUTECTIC 4 ® ) at the Bocagrande plant located in the city of Cartagena to spray commercial coatings such as 530AS ® , 560AS ® , and 140MCX ® . Its purpose is to combine this type of coating to increase the useful life of its naval components in terms of resistance to corrosion and wear, as is often performed in offshore installations with organic coatings, which provide sufficient protection against corrosion and are well-established for applications in marine environments, including post-treatments that increase corrosion resistance [19].…”

Machine Hammer Peening and Its Effect on the Surface Integrity of Arc-Sprayed WC-W2C-FeCMnSi Coatings

“…Conventional methods for reducing residual stresses, such as stress relief heat treatment, are only conditionally suitable for a broad range of tungsten carbide-based hard coatings and are not commonly used. Furthermore, as demonstrated for arc-sprayed metallic coatings (e.g., ZnAl coating), the MHP allows the densification of the coating's microstructure [52] and reveals the potential to increase the fatigue and corrosion fatigue resistance of the coating-substrate composite [53,54]. Among others, hybrid process strategies such as thermally assisted MHP are also being investigated to increase the capabilities of the machining process [52].…”