3822
The results revealed more uniformly distributed pitting attack on the corroded surfaces by increasing the heat-treatment temperature up to 300 °C , attributed to the more protective nature of the spontaneously air-formed passive layer on the surface of the alloy at initial immersion time .
 pitting, surfaces, temperature, layer, surface, alloy
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 pitting, surfaces, temperature, layer, surface, alloy