Metals and alloys used as part of prosthetic devices, artificial organs or implants, have to be highly corrosion resistant, good relevant mechanical properties and excellent biocompatibility with human body fluids and tissues, besides, wear and corrosion products have to be tolerable and harmless to the local sites tissue and fluids as well as human systems and organs. The literature and experience of many leading research laboratories, were surveyed concerning corrosion characteristics of different implanted alloys for varieties of applications in medical engineering applications, then a neutral (nonbias) and logical (scientific and practical) conclusions which are drawn and summarized as follows: Biocompatibility and highly corrosion resistant alloys, which satisfy the mechanical properties desired from the different implants applications are versatile, but the mostly used alloys are only few alloys namely (316L SS, CoCr, Ti and it's alloys, Nitinol and shape memory alloys) with specified preference for some applications related to corrosion resistance or other properties. There are other alloys which are classified as special purpose alloys as those as near heart sensors, leads, or electrodes _. etc, which are formed from other alloys or noble metals for obvious reasons. The few selected alloys used for their excellent corrosion resistance characteristics are summarized as follows: _ Stainless Steel 316L which is used as a femoral components in all patients and in different orthopedic temporary fixations. _ Co Cr Alloys are better corrosion resistance than SS 316L, and especially to chloride attacks (human body fluids). These alloys are also known to be most suitable for load bearing surfaces and superior fatigue and UTS strength. Titanium and Alloys known to have high specific strength excel any other implant materials especially when (Al and V) in the alloy are replaced by Nb, Zr, with different percentages. Nitinol alloys are other good corrosion resistance alloys and excellent biocompatibility and also possess a remarkable property of shape memory alloy with shape memory effects that promote several medical engineering applications. Modifications for above mentioned alloys due to some problems arose throughout their applications are proven to be very useful and important, and some times vital to be adopted and these are: a. Nitrogen surface coverage of Ti alloys and 316L alloys b. Using Nb and/or Zr instead of vanadium used in Ti alloys with different percentages. c. Addition of some alloying elements in Co-Cr alloys like Cu or N ion both to improve corrosion resistance. d. Passivation of the used alloys to minimize galvanic action when a composite of two metals are used in sensors, or Shape Memory Alloys, or two metals in contact when designing two metals joints. e. Ceramics or porous materials coating as a mean of surface modifications to enhance corrosion resistance or encapsulation. The specific application and relevant alloys, and effects of modifications used are mentioned in the different chapters of the work and summarized in the conclusions of this work, which is hoped to show a background for corrosion characteristics and evaluation for the different main alloys used and increasing applications as human body implants and prosthesis.