Question

1. Describe 3 different cases having corrosion by determining the material (the alloys with the codes and composition), describing the component having corrosion, the environment making corrosion to the component. You will give suggestions to the user that will solve the corrosion problem. However, there are some constraints that you need to check. - The reasons for the corrosion should be different for all cases. - The environment, the material, the component should be different for all situations. - The suggestions that solve the corrosion problem should be different for all situations. - There is no option for changing the material.

2. Write a question about composite materials and then solve the question. To do that follow the steps described below. - State the host material and fiber type. - State the composition of the composite material. - State type of fiber arrangement. - Give a reasonable modulus of elasticity for both of the materials. - State the cross-sectional area of the composite material. - State the direction of the fiber. - State the applied stress. After giving all these properties. -Compute the modulus of elasticity of the composite material. -Compute the loading carried by the fiber and the host material. -Compute the strain sustained by the fiber and the host material.

Answer 1

1) Answer:

Case 1(Galvanic Corrosion): The coupling of Fe(Area = 1cm2) and Cu (10cm2) in the normal atmosphere, Cu acting as cathode and Fe acting as the anode. The galvanic corrosion happens in this coupling because of electrode potential difference between these two metals and the rate of corrosion also very high in this case due to unfavorable area ration(area of anode is low compared to the area of cathode). The remedy for this is to increase the area of anode than the cathode.

Case 2 ( Pitting Corrosion): The 304 L Stainless Steel always prone to pitting corrosion in seawater solution. The Pitting corrosion starts initially when the damage of passive film on the stainless steel by the Chloride ions of the seawater. And when the Chloride ions damaged the passive film on the stainless steel, that damaged area acts as anode and remaining whole area acts as a cathode so these will be an unfavorable area ratio existed. The rate of pitting corrosion is very high and this is the main corrosion problem in almost all the industries. The remedy for this case is that usage of material in flowable seawater solution then there won't be any Chloride ions availability to damage the passive layer on the surface of stainless steel.

Table: The Chemical Composition of AISI Stainless Steel 304L

C	Si	Mn	S	P	Cr	Ni
0.03	0.42	1.43	0.0014	0.11	19.11	8.34

Case 3 (Erosion Corrosion): It is a degradation of the material surface due to mechanical action, often by impinging liquid, abrasion by slurry, particles suspended in fast-flowing liquid or gas, bubbles or droplets, cavitation, etc. SS 316L steel pipe carrying fuming nitric acid solution, the erosion-corrosion happens at curved sections of the pipe. The eroded part of the steel pipe acts as anode and tends to rapid corrosion at this place. The remedy for this is changing the designs of the pipe, like changing the sharp corners to the shallower curved corners so that it will decrease the impingement of liquid on the steel so that it can be possible to lower the effect of erosion-corrosion.

Table: The composition of AISI 316L Stainless Steel:

Sample(wt%)	C	Mn	Si	P	S	Cr	Ni	Mo	Al
AISI 316L	0.02	1.35	0.43	0.03	0.008	16.78	10.12	2.13	0.002

2) Answer:

Question about Composite: A Continous and aligned fiber-reinforced composite consists of 40 Vol% of glass fibers having a modulus of elasticity of 69 GPa and 60 Vol% of polyester resin that, when hardened, displays a modulus of 3.4 GPa. a) Compute the modulus of elasticity of this composite in the longitudinal direction, b) If the cross-sectional area is 250 mm2 and stress of 50 MPa is applied in this longitudinal direction, compute the magnitude of the load carried by each of the fiber and matrix phases. c) Determine the stain that is sustained by each phase when the stress in part (b) is applied.

Solution: