In normal mechanical and structural engineering design materials are selected primarily for their mechanical properties-corrosion is not an important criteria. The systems are generally protected against corrosion by surface coatings. Most machines are located indoors and are accessible for inspection and maintenance. The exceptions to this are machines used for construction and agriculture. These machines may well be used in corrosive environments but they are generally regularly maintained and some level of corrosion is acceptable.
In process engineering corrosion is a very important design factor and material are selected primarily on their corrosion resistance properties. Surface coatings are often not considered because of the risk of contaminating the process stream.
Metal Corrosion Properties – Non Chemiscal Environments
Ratings 0 = Unsuitable, 1 = poor, 2 = Fair, 3 =Fair to Good, 4 good, 5 = good to excellent, 6= excellent. Fresh WaterSea WaterSteamSteam Cond’teAirMetalStatic/TurbStatic/TurbDryWetCity/IndustGrey Cast Iron- Plain or Low Alloy4/34/3443Ductile Iron (High Strength )4/44/2443Cast Iron Ni_Resist. (14% Ni, 7% Cu, 2% Cr bal Fe)5/55/5554Ductile Iron Ni_Resist. (24 % Ni, bal Fe)5/55/5554Mild Steel- Low Alloy steels4/34/2443Stainless Steel Ferritic (17% Cro)4/61/4653Stainless Steel Austenitic (18% Cro ,8% Ni )6/62/5654Stainless Steel Austenitic (18% Cro 12% Ni, 2.5% Mo )6/63/5666Stainless Steel Austenitic (20% Cro 29% Ni, 2.5% Mo,3.5% Cu )6/64/6666Hastelloy Alloy (55% Ni, 17% Mo,16% Cr, 6% Fe, 4% W)6/66/6666Inconel (78% ni,15% Cr, 7% Fe)6/64/6666Copper Nickel alloys (Up to 30% Ni)6/66/6565Monel 400 (66% Ni, 30% Cu, 4% Si)6/66/6665Nickel Commercial (99% Ni)3/56/6664Copper and Silicon Bronze6/54/1565Aluminium Brass6/64/5565Bronze (88% Cu,5% Sn,5% Ni,2% Zn)6/65/5565Aluminium Alloys4/50-5/4255Lead (Chemical or antimonial)6/55/3025Silver6/65/5566Titanium6/66/6566Zirconium6/66/6566
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