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Corrosion Control Through Organic Coatings P04

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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. | 4 Blast Cleaning and Other Heavy Surface Pretreatments In broad terms pretreatment of a metal surface is done for two reasons to remove unwanted matter and to give the steel a rough surface profile before it is painted. Unwanted matter is anything on the surface to be painted except the metal itself and in the case of repainting tightly adhering old paint. For new constructions matter to be removed is mill scale and contaminants. The most common contaminants are transport oils and salts. Transport oils are beneficial until you want to paint salts are sent by an unkind Providence to plague us. Transport oil might be applied at the steel mill for example to provide a temporary protection to the I-beams for a bridge while they are being hauled on a flatbed truck from the mill to the construction site or the subassembly site. This oil-covered I-beam unfortunately acts as a magnet for dust dirt diesel soot and road salts anything that can be found on a highway will show up on that I-beam when it is time to paint. Even apart from the additional contaminants the oil picks up the oil itself is a problem for the painter. It prevents the paint from adhering to the steel in much the same way that oil or butter in a frying pan prevents food from sticking. Pretreatment of new steel before painting is fairly straightforward washing with an alkali surfactant rinsing with clean water and then removing the mill scale with abrasive blasting is the most common approach. Most maintenance painting jobs do not involve painting new constructions but rather repainting existing structures whose coatings have deteriorated. Surface preparation involves removing all loose paint and rust so that only tightly adhering rust and paint are left. Mechanical pretreatments such as needle-gun and wire brush can remove loosely bound rust and dirt but do not provide either the cleanliness or the surface profile required for repainting the steel. Conventional dry abrasive blasting is the most commonly .