How cavitation can occur and what impact it has on the cooling system?
An increase in air bubbles in a cooling system can increase the potential for cavitation erosion (pitting) of metal surfaces. Increased air can enter the cooling system through cooling system leaks and/or a faulty radiator cap.
What are the effects of corrosion on the radiator of a light vehicle cooling system?
The impact of corrosion Reduced corrosion protection (if the damage is not already severe) Reduced performance and cooling efficiency. Weak and brittle tubes. Loss of coolant/leakage.Aug 3, 2020
What is cavitation in the cooling system?
Cavitation is the formation of vapor bubbles in the cooling system and their subsequent implosion. Vapor bubbles form in the coolant when the coolant temperature increases, coolant pressure drops or a combination of a decrease in pressure combines with an increase in temperature.
What causes electrolysis in cooling system?
Electrolysis damage in an engine cooling system is caused by unintended electrical currents that flow from voltage differences that exist in the engine coolant jacket, the radiator, and the heater core. The damage can include rapid corrosion, pitting, flaking, and pinholes.
What is electrolysis in a radiator?
Electrolysis is caused by excess electrical current flowing through the system's cooling fluid or metal in finding a path to an electrical ground. When a radiator is not properly grounded, the cooling system collects stray electricity and the coolant becomes an electrolyte.
What causes radiator corrosion?
The most common cause of corrosion in your radiator system is sludge, a black, mud-like substance which, if untreated, will build up over time. From the inside of your radiators, it will cause rusting which end up eating tiny holes in the radiator resulting in leaks.Jan 20, 2017
How is cavitation formed?
Cavitation occurs when a pressure drop occurs within a region of a fluid to a point below the vapor pressure of the fluid at the current temperature. At this point, the state change from liquid to gas occurs, creating a bubble.Oct 16, 2019
Can cavitation cause overheating?
Signs of Cavitation in Pumps The typical symptoms will be overheating and possibly leaking from the weep hole of the water pump. In some cases, the impeller will separate from the shaft. It is not until you remove the pump that the full extent of the damage is revealed.
What does coolant nitrate do?
Nitrate: A corrosion inhibitor that protects several metals including iron and aluminum protection. pH: A scale to tell if coolant is acidic, neutral or basic.
How corrosion occurs in the cooling system?
The most serious form of galvanic corrosion occurs in cooling systems that contain both copper and steel alloys. It results when dissolved copper plates onto a steel surface and induces rapid galvanic attack of the steel.
What is the greatest single cause of electrolysis in a cooling system?
Is caused by: When the antifreeze turns bad or electrolysis occurs it leeches off very small particles of metals, rust and aluminum oxide into the coolant. Tests show these particles are like having liquid sandpaper flowing through your cooling system which in turn erodes the aluminum components even more.
Does coolant cause corrosion?
Antifreeze should not corrode metal parts, attack rubber, become viscous at low temperatures, or evaporate readily at the ordinary engine operating temperature.
What is the process that results in the inter-conversion of chemical substances?
process that results in the inter-conversion of chemical substances or a process that leads to the transformation of one set of chemical substances to another. Classically, chemical reactions create changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds.
What happens when air bubbles pound against the wall of the casting and the water pump?
This action erodes the protective film formed by the coolant, revealing the unprotected surface underneath. The corrosive action then begins.
Does stray current exist?
Yes, stray current does exist, but in a very small percentage of cooling system failures. In the majority of cases the system failure is man made, meaning that it is created by incorrect repairs after an accident or poor workmanship around the immediate area of the cooling system.
What is the driving force of galvanic corrosion?
The contact must be good enough to conduct electricity, and both metals must be exposed to the solution. The driving force for galvanic corrosion is the electric potential difference that develops between two metals.
What is corrosion control?
Control of Corrosion. Corrosion can be defined as the destruction of a metal by chemical or electrochemical reaction with its environment. In cooling systems, corrosion causes two basic problems. The first and most obvious is the failure of equipment with the resultant cost of replacement and plant downtime.
What are the factors that affect corrosion?
The success of cooling water corrosion inhibitor programs is affected by the following factors: 1 Water Characteristics. Calcium, alkalinity, and pH levels in water are important factors for reasons already cited. Further discussions are covered in the chapters on once-through and open recirculating systems. 2 Design Considerations. Low water velocity, which occurs in shell-side cooling, increases deposition. This factor must be addressed in the design of the system. 3 Microbiological Control. An effective microbiological control program is necessary to prevent severe fouling problems. Fouling caused by uncontrolled biological growth can contribute to corrosion by one or more mechanisms. 4 System Control. Even the best treatment technology available will fail without a reasonable level of control. Therefore, careful consideration must be given to system control-the accuracy with which the pH, inhibitor levels, and other water character-istics are maintained. 5 Pretreatment. Grease and/or corrosion products from previous treatment programs should be cleaned out, and the system should be treated with a high level of a good inhibitor before normal operation. 6 Contamination. Contamination can also be a problem. Sulfide, ammonia, and hydrocarbons are among the most severe contaminants. Sulfide is corrosive to steel and copper alloys. Ammonia is corrosive to Admiralty and promotes biological growth. Hydrocarbons promote fouling and biological growth.
How does pitting occur?
Pitting occurs when anodic and cathodic sites become stationary due to large differences in surface conditions. It is generally promoted by low-velocity or stagnant conditions (e.g., shell-side cooling) and by the presence of chloride ions. Once a pit is formed, the solution inside it is isolated from the bulk environment and becomes increasingly corrosive with time. The high corrosion rate in the pit produces an excess of positively charged metal cations, which attract chloride anions. In addition, hydrolysis produces H + ions. The increase in acidity and concentration within the pit promotes even higher corrosion rates, and the process becomes self-sustaining. Inhibitors can be used to control pitting, but they must be applied correctly.
Where does corrosion occur?
Corrosion occurs at the anode, where metal dissolves. Often, this is separated by a physical distance from the cathode, where a reduction reaction takes place. An electrical potential difference exists between these sites, and current flows through the solution from the anode to the cathode.
What is the pH of a cathodic reaction?
However, as pH decreases, this reaction becomes more important until, at a pH of about 4, it becomes the predominant cathodic reaction.
How to prevent crevice corrosion?
The best way to prevent crevice corrosion is to prevent crevices. From a cooling water standpoint, this requires the prevention of deposits on the metal surface. Deposits may be formed by suspended solids (e.g., silt, silica) or by precipitating species, such as calcium salts.