Study of the Effects on Plain Bearings in Simulated Corrosion Tests Using Carbon Neutral Fuels

<div class="section abstract"><div class="htmlview paragraph">Many countries around the world are currently working toward carbon neutrality, which would reduce greenhouse gas emissions to net zero by 2050. To achieve carbon neutrality, the search for new fuels to replace gasoline has been active. This study focuses on hydrogen and methanol fuels and examines their effects on plain bearings when these fuels are used in internal combustion engines. Compared to gasoline, these fuels differ significantly in the composition of gases produced after combustion. It is assumed that nitric acid, etc. will be mixed in the engine oil when hydrogen is combusted whilst formic acid, etc. will be mixed in the engine oil when methanol fuel is combusted. For this reason, corrosion tests were conducted by adding nitric acid or formic acid solution to the engine oil then placing plain bearings in the deteriorated oil. The results confirmed that significant corrosion of the bismuth overlay coating occurred and subsequently the performance of plain bearings may deteriorate due to the loss of the overlay coating. As a countermeasure, corrosion tests were conducted using the corrosion resistance enhanced coating. In the presence of enhanced overlay coating, the corrosion was largely prevented, confirming the excellent chemical stability of the newly developed plain bearing. In addition, a decrease in oil TBN was observed with an increase of added nitric acid, whilst a decreased of oil additive components was observed with an increase of added water. These results suggest that it is possible to produce intentionally degraded oil by adding acid and water to the oil. Similarly, corrosion tests were conducted with the addition of formic acid, and no corrosion was observed on various plain bearings. However, test conditions were limited and further research is needed in this area.</div></div>