Research Information System
Thesis Type: Postgraduate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2022
Thesis Language: Turkish
Student: Burhan GÜVEN
Supervisor: Nursel Dilsiz
Abstract:
High strength aluminum alloys are widely used in aviation and aerospace industries because of their desirable strength/weight ratio that results from the alloy addition (e.g., Cu, Fe etc). However, this alloy addition causes pitting corrosion of the aluminum surrounding those intermetallic contents. An effective way to prevent corrosion is a protective coating system that includes topcoat, primer and conversion coat. The conversion coating is in direct contact with the alloy surface and is expected to provide both good corrosion protection and an adhesion surface. The chromate conversion coating (CCC) has been widely used in aviation/aerospace industry and provides excellent active corrosion protection and adhesion to aluminum alloys. Unfortunately, the Cr(VI) is toxic and chromate is a carcinogen. Therefore, trivalent chromium process coating (TCP) and chrome-free coatings are being developed to replace CCC.In this thesis, compared with today's widely used Cr containing CCC,the corrosion resistance, coating thickness, resistance to electrical conductivity and paint adhesion performance of TCP coating (Cr (III) content) and chromium-free coating on three high strength aluminum alloys (2024-T3, 6061-T6 and 7075-T6) were investigated. These performance parameters were compared with the methods specified in the MIL-DTL5541/81706 standard. In addition, the surfaces of 2024-T3 alloys coated with TCP, chromium-free coating and CCC were examined with a scanning electron microscope (SEM) and compared with uncoated panels. As a result of the tests, it was seen that TCP coating (Cr (III) content) provides better corrosion protection compared to CCC's other Cr-free alternative silane-containing conversion coatings. The corrosion performance of the TCP coating provided good corrosion protection for all three aluminum alloys when compared to chromium-free coatings.
KeyWords : Chemical surface treatment, metallic surface coating, chemical
conversion coating, corrosion, chrome free coating, silane