IOSR Journal of Engineering (IOSRJEN) www.iosrjen.org ISSN (e): 2250-3021, ISSN (p): 2278-8719 Vol. 04, Issue 02 (February. 2014), ||V2|| PP 34-39 International organization of Scientific Research 34 | P a g e Ship hull corrosion caused by default and lack of maintenance on the impressed current cathodic protection Fernando B. Mainier 1 , Vitor Perassolli 2 1 Escola de Engenharia, Universidade Federal Fluminense, Niterói, RJ, Brazil, 2 Posgraduação em Engenharia Civil, Escola de Engenharia, Universidade Federal Fluminense, Niterói, RJ, Brazil, Abstract: - This article presents a case study of corrosion of a ship hull that began after continuous failure of the impressed current cathodic protection system. The purpose of this article is not to question or criticise the design, installation, maintenance, or operation of the cathodic protection system, but only to show through the inspection carried out that the main aspects of the corrosive process that occurred when it was anchored for more than six months. In order to leave the ship in normal operating conditions, repairs were conducted that consisted of cleaning with pressurised water blasting, welding repair of corroded plates, paint application, and installation of zinc anodes in cathodic protection replacement. Keywords: - Cathodic protection, corrosion, failure, ship hull, zinc anode I. INTRODUCTION The study of corrosion and anti-corrosion protection technique development began in the 19th century and continues to this day. However, corrosion and corrosion protection are known to be associated with a range of disciplines extending from chemistry to human behaviour. Corrosion is defined as the deterioration of material by chemical or electrochemical actions of a corrosive medium. Due to this, corrosion is a permanent challenge to man, because when more science creates and develops and the technology applies and advances, the more she finds spaces and ways of doing this. Generally speaking, we can say that a corrosive attack carries considerable costs, which may, in certain cases, include environmental pollution, compromise the operational safety of the equipment, and promote catastrophic accidents and the loss of human life. Problems associated with corrosion due to seawater have been studied for many years, but despite the published information about the behaviour of materials in seawater, failures still occur. The corrosion rates of carbon steel range from 0.20 to 2.0 mm/year depending on several factors, such as oxygen, pH, contaminants, macro-, and micro-organisms. Some of these factors are interrelated and depend on physical, chemical, and biological variables, such as depth, temperature, nearby rivers, contamination by industrial effluents, and the availability of nutrients [1, 2]. The interaction between biological activity and steel performance is very important in seawater. Depending on the contact time, the macro fouling, such as barnacles and mussels, can be either protective or result in accelerated corrosion depending on the area of steel exposed and the extent of the amount of biological fouling. The corrosion of carbon steel in seawater can occur under various forms: localised, generalised, plates, pitting, and considering the properties of seawater are common, the occurrence of corrosion by differential aeration, crevice corrosion, and corrosion under deposits. Anticorrosive protection of ships and maritime facilities is generally accomplished through cathodic protection by application of coatings that resist the aggressive action of seawater. Currently, the cathodic protection of ships is made of cathodic protection with galvanic anodes (aluminium or zinc) or impressed current cathodic protection. Cathodic protection of small boats is simple, but medium and large ships are more complex and require very specific plans. The principles of this technology come from the past. It is believed that the first ship to use the cathodic protection was during the Sammarang Sea voyage to Nova Scotia in 1824–1825 [3]. Systems using galvanic (sacrificial anodes) for current cathodic protection are provided by the potential difference that exists between the galvanic anode (aluminium, magnesium, or zinc) and the carbon steel structure. In cathodic protection of a metallic structure, the flow of the electric current is provided by the potential difference between the metal surface to be protected and the anode, which has a more negative potential, according to the following electrochemical reactions: Anodic: Zn – 2 e - → Zn 2+ Cathodic: H 2 O + ½ O 2 + 2 e - → 2 OH - (aerated seawater) Figure 1 represents the system of protection by galvanic anodes (zinc) for ship hull (carbon steel) protection.