The industry standard in fireside erosion/corrosion control
Fireside corrosion of the waterwall panel is among the most expensive repair/replacement for a boiler operator. AZZ Specialty Welding developed Unifuse180® technology for mitigation, and over the years, this process has become the industry standard in fireside erosion/corrosion control.
In coal-fired boilers, the primary damage mechanism is sulphidation attack. Although fireside corrosion is found in all boilers, the accelerated thinning of coal-fired boiler waterwalls became a critical issue when the combustion chemistry of boilers was changed to address the formation of Nitrous Oxides (NOx) during combustion. By installing LoNOx burners, which change the combustion atmosphere in the furnace box to a reducing atmosphere, NOx compounds were reduced. But this change significantly accelerated the waterwall wastage caused by corrosion.
AZZ | WSI Unifuse180® has the largest installed base in the world for the mitigation of fireside corrosion in critical as well as sub-critical, coal-fired units. The product can be field applied when existing waterwall panels need protection, or can be shop applied for new construction or waterwall change-outs when the existing base material is beyond repair.
In Waste to Energy Boilers (WTE) the primary damage mechanism is caused by heavy metals that react with chlorine to form low melting point chlorides. In 1985 AZZ WSI developed a weld metal overlay process utilizing alloy 625 that provided a revolutionary technology for the mitigation of fireside corrosion in these boilers. With a true welded bond, the coating cannot disbond from the boiler base material so it can withstand the thermal cycling caused by changes in operating load and other contributors such as soot blowers. As a welded coating, the protective barrier does not have any porosity or other imperfections that would allow the corrosive environment to penetrate the barrier and create base metal damage.
The field applied corrosion-resistant weld metal overlay (Unifuse180®) originally developed by AZZ Specialty Welding for waste to energy boilers has proven to be the most reliable method for the mitigation of fireside thinning. With a true welded bond, the coating cannot disbond from the boiler base material, so it can withstand the thermal cycling caused by changes in operating load and other contributors, such as soot blowers. As a welded coating, the protective barrier does not have any porosity or other imperfections that would allow the corrosive environment to penetrate the barrier and create base metal damage.
Shop production services
As a global organization, AZZ Specialty Welding maintains two production facilities (USA and Europe) for the application of Unifuse180® weld metal overlay. Our resources and expertise enable us to handle the largest and most complex panel configurations in the world for customers who are individual plant operators as well as boiler original equipment manufacturers. AZZ Specialty Welding offers an unrivaled fabrication resource. We can handle large panels up to 18 m long and 2 m wide, giving you a lower cost per panel. Plus, we can apply an overlay thickness of 1.2–3 mm, or even more, to suit your specific requirements.
Field production services
Field applied waterwall overlay is performed by AZZ | WSI’s field application specialists. AZZ | WSI is the world’s largest provider of weld metal overlay with global application resources. With the largest fleet of equipment and trained personnel in the industry, no application project is too big to handle.