tailieunhanh - CORROSION RESISTANCE_2

Tham khảo sách 'corrosion resistance_2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 11 Corrosion Behavior of Stainless Steels Modified by Cerium Oxides Layers Emilia Stoyanova and Dimitar Stoychev Institute of Physical Chemistry Bulgarian Academy of Sciences Bulgaria 1. Introduction The modifying of the surface which involves altering only the surface layers of a material is becoming increasingly important with the aim to enhance the corrosion resistance of many kinds of materials. The advantage of this approach lies in the fact that the natural physical and mechanical properties of the material are retained while at the same time the corrosion resistance is increased. It is well known that electroplated zinc coating is employed as active galvanic protection for low and middle-content alloyed steels Almeida et al. 1998 Hagans Hass 1994 Kudryavtsev 1979 Lainer 1984 Zaki 1988 . However zinc is a highly reactive element and therefore high corrosion rates of this coating are observed in cases of indoor and outdoor exposures. For this reason a post-treatment is needed to increase the lifetime of zinc coatings. This kind of treatment is applied in the current industrial practice to prolong the lifetime of zinc coatings and the steel substrates respectively. This treatment consists of immersion in a chemical bath which forms a conversion layer over the plated zinc. The so formed layer is a dielectric passive film with high corrosion resistance and it is also a better surface for paint adherence Zaki 1988 . The main problem with the traditionally applied post-treatment procedures is the presence of Cr6 salts that are considered to be carcinogenic substances which are known to be very harmful to human health and environment Schafer Stock 2005 and whose use is forbidden by European regulations Hagans Hass 1994 . Molybdates tungstates permanganates and vanadates including chromium-like components were the first chemical elements to be tested as hexavalent chromium substitutes Almeida et al. 1998a 1998b Korobov et al 1998 Schafer Stock 2005 Wilcox Gabe 1987 .

• Cơ khí - Chế tạo máy
• Corrosion Resistance
• Zinc Aluminum Matrix
• Systematic Study
• Semiconductor Silicon
• Wafer Fabrication
• Material Behavior