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Evaluation of ceramic sacrificial coatings for improved alkaliinduced corrosion protection in biofuel-fired boilers

R. Pompe ; L. Eklund ; Lars-Gunnar Johansson (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; O. Lyckfeldt ; Jan-Erik Svensson (Institutionen för kemi- och bioteknik, Oorganisk miljökemi)
Corrosion 2013; Orlando, FL; US; 17-21 March 2013;(NACE - International Corrosion Conference Series ) (0361-4409). p. (9 pp). (2013)
[Konferensbidrag, refereegranskat]

In the combustion of bio-based fuels the critically exposed burner parts in small boilers are typically uncooled and are usually made of FeCrNi alloys. These materials can suffer attack from the ashes because of the formation of alkali chromate. The reaction depletes the protective oxide in chromia, leading to accelerated corrosion. Selected "acidic" ceramic coatings based on Ti, Si, B and P have been evaluated for use as sacrificial layers to prevent the initial reaction of alkali and chromium. An accelerated oxidation test method including mild thermal shock has been utilized that previously proved useful to provide application-relevant results. A comparison of coated and uncoated specimens was performed with an austenitic high temperature steel as a substrate. The results indicate that the alkali released from the ash reacts with the respective "acidic" elements in the deposited coatings. This reaction has promoted initial formation of a thin and continuous chromium-rich protective oxide sub-layer. In addition, the oxide scale formed on the coated specimens appeared more coherent and crack-free. A significant enrichment of Ni at the steel-oxide interface also occurred that can promote high temperature corrosion resistance.

Nyckelord: Alkali corrosion, Bio-fuel, Coatings, High temperature corrosion-resistant alloys, Pellet ash, Residential boilers, Screening, Thermal shock, Accelerated corrosion, Accelerated oxidations, Deposited coatings, High temperature corrosion resistance, Protective oxides, Sacrificial coatings, Steel-oxide interfaces, Biofuels, Ceramic coatings, Chromium, Corrosion resistance, Corrosion resistant alloys, Scale (deposits), Testing, Boilers



Denna post skapades 2015-05-06. Senast ändrad 2016-04-29.
CPL Pubid: 216547

 

Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)

Ämnesområden

Materialteknik
Naturresursteknik

Chalmers infrastruktur