Protect bolts and nuts from corrosion
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4 Ways To Combat Corrosion And Make Your Pumps, last longer
If you’re buying a new pump, while making a decision on the best option for your industry, select based on ability to resist corrosion and total cost of ownership (remembering to calculate cost to include initial cost, maintenance and replacement costs, downtime and life expectancy).
Here are some ideas to prevent and address corrosion in pumps.1. Select the right pump
Aggressive fluids like acids, wastewater effluents and others require careful selection of material. Getting the right material can prevent the premature replacement of pumps and cut on valuable time lost. Plastic and metal are the two most common materials used for pumping these liquids. Carefully consider the properties of your liquid and make a selection from the various types on offer. In looking for options for material, look for a consensus from professionals on a particular material for your needs. Chances are if several people are recommending it for you, it’s the right choice.2.Consider coating technology
A useful method of dealing with corrosion is coating. Coating ‘is the thin layer of a covering substance… applied on a surface… to improve its critical properties and to create a protective barrier against deterioration’ Even the best choice of material is susceptible to corrosion so a coating will help to increase life. A wide range of coatings is available for pumps. Speak to your engineer about the kind of use your pump will have and get recommendations.3.Run your pumps slower
The corrosion created by abrasive liquids can often be significantly reduced when a pump runs slower. Pump manufacturers often recommend speeds that are less than half the capacity to help pump last much longer, depending on the nature of the liquid within. Also, test periodically to see what the condition of the pump is. Be sure to do any testing for corrosion in the same conditions under which the pump actually runs.4.Protect the external parts of you pump
It’s not just the inside that needs protection; the surfaces exposed to the outside also need to be protected from corrosion. These parts are not directly exposed to the fluids being pumped but are often subject to damage especially in cases where the pump is submerged – for example when you’re pumping from the sea and need saltwater protection. Coatings are available for external surfaces as well, most often in the form of paint, which can repel water and other contaminants. HOWEVER, painting is just short term remedy. Nitto Denko’s anti-corrosion XG Tape series will provide you with a cost-effective and comprehensive solution. Start early when you’re thinking about the issue of pumps and corrosion since defence is the best form of offence in protecting from harsh liquids. A clear discussion of your needs with a competent and established anti-corrosion tape manufacturer is usually a good place to start. By VTS team
What is Corrosion | 4 typical types of corrosion
According to the Kennedy Space Center, corrosion can be defined as the deterioration of a material due to a chemical reaction with its environment over time. Metals corrode because they’re used in environments where they’re naturally unstable; and it’s a big problem for bridge, pipeline, plant builders and other architects who frequently use metal products in their structures.
There are various forms of corrosion. Below is a selection of just three forms of corrosion.
Uniform Corrosion
Let’s start with the basic form of corrosion first. You can think of uniform corrosion as rust, since it is the most common form of corrosion. And since rust is pretty common; it’s not a huge issue for architects to take care of. Using protective coatings like paint or a sealant can control uniform corrosion for short term but for long term control, a comprehensive solution is required. See how corrosion is prevented.Galvanic Corrosion
Galvanic corrosion occurs when different metals come into contact with each other. This form of corrosion can easily be spotted where the two metals meet. Popular trinkets like insulating gaskets and washers can assist with staving off galvanic corrosion; but they will need to be replaced with regular maintenance.Concentration Cell Corrosion
Concentration cell corrosion occurs when two or more areas of a metal surface are in contact with each other; but corrode at different rates. There are three general types of concentration cell corrosion: Metal Ion Concentration Cells: This happens most commonly in water when a high concentration of metal ions are exposed crevices and become corroded over time. This can be prevented by sealing the exposed crevices to prevent water from coming into contact with the metal.- Oxygen Concentration Cells: This type of corrosion can occur in areas with low oxygen; like underneath wood, rubber, tape, and other materials. This can be minimized by sealing the exposed areas; keeping the surfaces clean, and avoiding materials that will create moisture between surfaces.
- Active-Passive Cells: Some metals actually depend on thin films of corrosion product, called an active-passive cell, for corrosion protection. If this thin film is broken, the metal beneath the film will start to corrode. This type of corrosion can be avoided with regular cleaning and application of protective coatings
Understanding Corrosion and How to Protect Against It
- Direct loss or damage of metal structures due to corrosion. An example is a hot water tank that has corroded and must be scrapped.
- Maintenance costs attributed to corrosion. Any metal surface that must be painted every few years to control corrosion falls into this area.
- Indirect losses resulting from corrosion. These losses may result from leakage and fires. Explosions attributed to leakage, power failures, facility shutdown and labor losses are also indirectly the result of corrosion.
What is rust?
When iron or steel corrodes, the result is iron oxide, or what we call rust. Steel is mostly composed of iron ore. In its natural state, iron ore looks much like rust: dark red and finely grained, with a tendency to hold moisture. Iron ore is a stable substance until it is converted into iron or steel, naturally weaker elements. When steel is exposed to moisture and oxygen, it immediately starts regressing to its natural state. Although protective measures have been taken, a large part of the steel made in this century has already rust back to an oxide, its natural state. Three elements are required for corrosion to exist: a protected metal, a corroded metal, and a current-conducting medium between the two. When two dissimilar metals are brought into contact, one will become the protected metal, and the other will become the corroded metal. Plant operators may recognize environmental situations that are conducive to corrosion.For example:
- If galvanized fittings are used on steel pipe, the galvanized (zinc) fitting will become corroded, while the steel remains protected.
- Steel or other metals under stress will become corroded, while the unstressed steel is protected from corrosion. This is the reason you see rust pitting on steel.
- Freshly cut steel will corrode more rapidly. Threads cut on pipe will always rust first.
- Adding salt to water greatly enhances its current-carrying ability. Thus, steel exposed to seawater or salt spray will corrode more rapidly than steel in fresh water. Atmospheric corrosion is greater in areas near the oceans, due to the effect of salt air. Concentrated brine solutions, such as those used in the food-processing industry, cause severe corrosion.
- Industrial smoke and fumes contain acids, alkalies and other chemicals, which serve as current conductors. Consequently, atmospheric corrosion in industrial areas is more severe than in rural areas.
- Soil, clay and earth materials are also good conductors of electricity. Pipelines and other steel buried in the ground will be prone to corrosion unless protected. Just as soil varies considerably in composition, it also varies in its electric conductivity: some soils cause more severe corrosion than others.
Corrosion control
To make the use of steel and other metals practical in construction and manufacturing, some corrosion-protection practices must be employed. Otherwise, the life of steel and other metals will be limited, reducing efficiency and escalating the cost of maintenance. There are several effective ways to stop corrosion:- Impressed current. By using suitable current-generating equipment and controls, it is possible to reproduce a current equal in strength to the corroding current, but flowing in the opposite direction. This type of protection is generally limited to pipelines, buried tanks, etc., and requires careful engineering and layout. Used improperly, an impressed current can promote corrosion.
- Sacrificial metals. Steel can be protected by adjacent placement to a dissimilar metal. For example, if zinc or magnesium is placed in direct contact with steel, it protects the steel from corrosion. Here, zinc and magnesium serve as sacrificial metals that not only protect the area of immediate contact, but also protect beyond the metal in each direction. Protection from rust by sacrificial metals is commonly used in several forms:
- Zinc or magnesium blocks are often used to protect ship hulls, water tank interiors and other submerged surfaces.
- Complete covering of the steel with the sacrificial metal is often done. Galvanized steel, for example, is steel covered with zinc. The zinc is sacrificial and will protect the base steel.
- Zinc-rich coatings may be applied to a steel surface to provide cathodic protection. Zinc-rich coatings consist of 85% to 95% zinc metal in a suitable binder. The zinc particles, deposited by painting, protect the steel.
- Primers. Primers and finished coatings protect metal surfaces by providing a barrier between the steel and the corroding elements. They also prevent moisture from reaching the surface of the steel. A coating film protects underlying metal substrates in three ways:
- Coatings can slow the rate of diffusion of water and oxygen from the environment to the metal surface. This slows the corrosion process.
- The paint film can slow the rate of diffusion of corrosion products from the metal surface through the paint film. This also slows the corrosion process.
- The anti-corrosive pigments contained in quality primers change the surface properties of the base metal. The metal develops a high electrical resistance as a result. Different pigments accomplish this reaction in different ways. Primers absorb and tie up moisture so that it does not react with the steel.
The product has 4 components:
- Primer Nitohullmac XG-PN: a synthetic fluid and a paste of non-solvent type primer that consists of rust preventatives, inert inorganic fillers and coloring agents etc. It has good waterproofing performance, inhibit rust advance by permeating rust layer because it is oil type.
- Outdoor anti-corrosion tape:made of plastic base non-woven fabric implemented with a compound which has a specially compounded drying oil as its main ingredient, form anti-corrosion layer, good weatherbility, can shut out water and air that will lead to corrosion of metal surface of cause of good adhesive tape compound and primer
- Nitohullmac XG Filler material Nitohullmac XG-M: a clay-like filler material added inert inorganic fillers and thickener, can be used as gap filler materials for irregular shaped parts like flange or valve; and
- Top coat Nitohullmac XG-T: a water based top coating material to improve outside appearance, durability and waterproofing performance for XG tape.
Corrosion in the electric power industry
Corrosion, the plant operators’ headache
Corrosion in the electric power industry results in loss of millions of US$ annually. The revelations come at a time when plants are working to enhance efficiency and shorten the offline maintenance timeline. Corrosion prevention techniques can go a long way to improve the life of various machinery components and enhance plant safety.
The most common types of corrosion issues in thermal plants include erosion, oxide corrosion and galvanic corrosion. Erosion arises when an aggressive chemical environment comes into contact with high fluid surface velocities thereby increasing surface wear outside the protective coating or scale area. With oxide corrosion, the electrochemical process arises when metal is exposed to water causing the composition to change. The galvanic corrosion process, on the other hand, occurs when two dissimilar metals come into contact. When that happens, the effect is an electrical reaction that accelerates corrosion. Thermal power plants, whether coal, solar thermal electric, nuclear or geothermal plants operate by generating steam that drives turbines that turnaround electrical generators to produce power. There are several components in the thermal power plants that operate at different temperatures and pressures. These components include cooling tower, boilers, superheater, turbine and steel drums. When any of these components are exposed to corrosion, the system operation may be compromised causing serious safety hazard issues. This is especially true if a worker comes into contact with radioactive materials, gas and hot steam because of leaks or damage. Corrosion can also force the thermal power plant operators to grapple with non-operation delays even after scheduled maintenance is performed or be requested to pay nondelivery fees. Corrosion in thermal power plants can be prevented if the operators take into mind the following preemptive measures.- Ensure the generators operate under low humidity levels using a closed loop system
- Seal the turbine opening to keep it as tight as possible
- Use water conditioning agents to counter the presence of organic agents or chemicals that cause corrosion. The other strategy is replacing the steel components with a line of effective composites.
- Perform regular inspections and test components exposed to the risk of corrosion. The key focus areas include welded areas, ducts, pipes, and turbines.
- Install a windshield or protective liner on the cooling stacks to prevent thermal shock and chemical attacks.
- Install insulation materials with preventive coating or jacket on all vulnerable pipes. Also, consider improving the pipe design to counter corrosion.
Corrosion in plants | Issues and Nitto Denko XG Tape solution
Corrosion issues in plants prolongs maintenance, increases operating costs, reduces efficiency and poses safety risks to workers. To optimize equipment and machinery performance, corrosion prevention is vital. This means ensuring the successful installation of protective coatings on items that are susceptible to corrosion.
See more | All-round anticorrosion solutionTypes of Corrosion in plants
- Oxide corrosion: An electrochemical process on metal surfaces when oxygen molecules dissolve in water. This type of corrosion occurs when lagging isn’t installed properly, or when protective surface coatings fail or were never applied.
- Galvanic corrosion: A process that occurs when two dissimilar metals contact each other, creating an electrical reaction that promotes corrosion.
- Hot corrosion: Accelerated corrosion due to the presence of salt contaminants that form molten deposits, which damage protective surface oxides.
- Erosion: The combination of high fluid surface velocities and an aggressive chemical environment that wears away a surface’s protective scale or coating.
Plant Corrosion Danger Zones
- Hot and cold piping systems
- Boilers
- Pumping system
- Towers
- Bolts Plates
- Welding seams
- Bypass ducts
- Chemical storage tanks
- Fuel handling areas
- Collection sumps
The Consequences of Foregoing Corrosion Prevention in a Plant
- Safety risks: When corrosion affects systems carrying steam or hot water—such as pipes—material or welds may fail, causing bodily injury or death.
- Fouling: Power plant systems foul because of the ingress of moisture, dust or salt in the air.
- Pipe corrosion: Insulating with an outer finish or jacketing keeps water from contacting tank shells or pipes, preventing corrosion, pitting, cracking and failure.
- Contract-related fines: When corrosion affects a plant’s system, it may not start up after a maintenance outage, leading non-delivery fees for being out of service.
- Pollution control: Corrosion in tanks may hinder a plant’s attempts to control sulfur emissions in the environment. Chemical emissions lead to acid rain, which damages buildings and other structures in a plant.
- High maintenance costs: Corrosion can account for up to 75 percent of a plant’s arrest time during maintenance and up to 54 percent of production costs.
- Gas or air leaks: Unaddressed plate corrosion leads to air or gas leaks. The problem generally occurs when the lagging system fails.
- Flue gas inlet duct problems: Gases within ducts attack the system physically and chemically.
