tailieunhanh - Corrosion Control Through Organic Coatings P08

Nhiều chương trình CAD hiện nay cho phép tạo ra các mô hình ba chiều để có thể nhìn từ mọi góc độ. Các chương trình CAD mô hình hóa vật thể đặc tiên tiến là một hệ thống thiết kế hiện thực ảo. Những mô hình đặc như vậy có thể được dùng làm cơ sở cho các phân tích phần tử hữu hạn (FEA) và / hoặc tính toán động lực dòng chảy (CFD) của thiết kế. Cho đến ứng dụng gia công với trợ giúp máy tính (CAM), những mô hình này cũng có thể được dùng. | Q Corrosion Testing Practice Corrosion tests for organic coatings can be divided into two categories 1. Test regimes that age the coating. These are the accelerated test methods including single stress tests such as the salt spray or cyclic tests such as the American Society for Testing and Materials ASTM D5894. 2. Measurements of coating properties before and after aging. These tests measure such characteristics as adhesion gloss and barrier properties water uptake . The aim of the accelerated test regime is to age the coating in a short time in the same manner as would occur over several years field service. These tests can provide direct evidence of coating failure including creep from scribe blistering and rust intensity. They also are a necessary tool for the measurement of coating properties that can show indirect evidence of coating failure. A substantial decrease in adhesion or significantly increased water uptake even in the absence of rust-through or undercutting is an indication of imminent coating failure. This chapter provides information about Which accelerated tests age coatings What to look for after an accelerated test regime is completed How the amount of acceleration in a test is calculated and how the test is correlated to field data Why the salt spray test should not be used SOME RECOMMENDED ACCELERATED AGING METHODS Hundreds of test methods are used to accelerate the aging of coatings. Several of them are widely used such as salt spray and ultraviolet UV weathering. A review of all the corrosion tests used for paints or even the major cyclic tests is beyond the scope of this chapter. It is also unnecessary because this work has been presented elsewhere the reviews of Goldie 1 Appleman 2 and Skerry and colleagues 3 are particularly helpful. The aim of this section is to provide the reader with an overview of a select group of accelerated aging methods that can be used to meet most needs General corrosion tests all-purpose tests Condensation