Oxidation Resistance of the Coatings Obtained by Plasma Electrolytic Oxidation on Aluminium Alloys

Abstract

Plasma electrolytic oxidation (PEO) is one of the new methods of obtaining thin layer oxide ceramic coatings on machine elements of different purpose of use; that allows considerably increase their durability. This paper outlines the results of experimental studies on corrosion resistance of oxide ceramic coatings formed by PEO on various aluminum alloys using КОН-Н3ВО3 electrolyte. Corrosion tests of the samples were performed using the following two methods: 1. According to ASTM G44 “Standard Practice for Exposure of Metals and Alloys by Alternate Immersion in Neutral 3.5% Sodium Chloride Solution”, 2. Polarization tests. Both tests of corrosion resistance of aluminum alloys clearly demonstrate that plasma electrolytic oxidation significantly improves corrosion resistance: depending on an alloy, corrosion rates of PEO coated samples are by the factor of 2.5-80 lower as compared with non-coated samples.

Plazma elektrolitička oksidacija (PEO) je jedan od novih metoda za dobijanje oksidno keramičkih premaza u tankim slojevima na elementima mašina različite namene, što značajno produžava njihov vek trajanja. U ovom radu su izneti rezultati eksperimentalnih istraživanja otpora na koroziju oksidno keramičkih premaza nanetih pomoću PEO na različite aluminijumske legure upotrebom elektrolita КОН-Н3ВО3. Testovi korozije na uzorcima su izvođeni upotrebom sledeće dve metode: 1. Prema ASTM G44 “Standardna praksa za izlaganje metala i legura alternativnim potapanjem u neutralni 3.5% rastvor natrijum hlorida”, 2. Testovi polarizacije. Oba testa otpornosti na koroziju aluminijumskih legura jasno su pokazala da plazma elektrolitička oksidacija značajno poboljšava otpornost na koroziju: zavisno od legure, stepeni korozije PEO zaštićenih uzoraka su 2.5-80 puta niži u poređenju sa uzorcima bez premaza.