Molten Salts


 

Molten salts can be highly corrosive and cause problems for various engineering processes in energy, aerospace, and manufacturing industries.  Cerablak™ materials have demonstrated excellent resistance to molten salt attack, and several Cerablak™ product offerings are available for protection of metal, glass, and ceramic materials utilized in these harsh environments.

 

 

Corrosion from Molten Salts
Salts are often present as corrosive contaminants in many environments. Sources of salt include chlorides from ocean water and sea spray, sulfates and vanadate remnants from raw ore and crude oil extraction, and silicates from airborne sand and volcanic ash. These salts can find their way into combustion environments present in turbine engines, reciprocating engines, and coal-fired furnaces. These salts have a relatively low melting point and high chemical activity; thus, when salts interact with combustion environments they liquefy into an extremely corrosive fluid, strongly attacking expensive turbine alloys, ceramics, and ceramic coatings.  This attack leads to reduced material lifetimes and unpredictable material failure of expensive components.

 

 
Cerablak® Barrier Films for Advanced Corrosion Control

The Cerablak™ family of products has several offerings well suited to protect high-temperature materials from molten salt attack and corrosion.  As an advanced high-temperature stable glassy aluminophosphate material, Cerablak® surface treatments have proven to be an effective barrier under various molten salt corrosion conditions, able to protect metalglass, and ceramics in relevant engineering applications.  

 


Cerablak® UTF provides an ultra-thin (sub-micron), hermetic-quality barrier that is resistant to salts at high temperatures. A demonstration of protection of silica glass from molten salt attack is shown in the image above; the Cerablak® UTF-coated glass slide subjected to molten sodium sulfate is shown with no sign of attack on the underlying silica after 900°C heat treatment for 15h in the air.  Uncoated glass is immediately attacked by sodium sulfate, evidenced by the devitrification of the silica.

 


A highly innovative sealant solution has been developed using Cerablak® HTS for mitigating hot corrosion of ceramic thermal barrier coatings used on turbine parts of both aero and power generation gas turbine engines.  Operating turbines ingest sand and other airborne particulates, including volcanic ash; a critical component of these are calcium-magnesium-alumiosilicate materials (CMAS), which have melting points in a similar range to engine operating temperatures.  When CMAS becomes hot enough to liquefy, it attacks the internal engine component materials, including thermal barrier coatings (TBCs). Cerablak® HTS serves as a sacrificial barrier layer, covering internal TBC pore surfaces with a thin film and serving as a source of alumina, which prevents CMAS from melting and reacting with the fine-scale TBC microstructure.  Cerablak® HTS has shown to dramatically increase the resistance of TBCs to CMAS attack, allowing the TBCs to maintain high performance and last longer.