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<\/span><\/li><\/ul><\/div><\/div>Cortec<\/span>\u00ae <\/span><\/sup>Releases New Guide to Corrosion in the Pulp & Paper Industry<\/span><\/p><\/h1><\/div><\/div><\/div><\/div><\/div>
February 1, 2024<\/em><\/p>\n
Pulp and paper mills can be very corrosive environments, especially due to the chemicals often used for pulping. This takes a toll both on structures and equipment. Furthermore, when a plant shuts down, high dollar assets face another dimension of corrosion risk while idle. To address these concerns, Cortec\u2019s Technical Director \u2013 Energy & Engineered Solutions, Jim Holden, P.E., who has worked directly with paper mill asset preservation, has created a guide to corrosion in the pulp and paper industry.<\/span><\/p>\n
![\"pulp-paper-industry\"](\"https:\/\/www.cortecvci.com\/wp-content\/uploads\/pulp-paper-industry-1024x713.jpg\")
<\/p>\nPulp and Paper Overview<\/span><\/h2>\n
The guide starts with an overview of pulp and paper mill processes, equipment, and general corrosion threats. It then identifies specific areas where protection may be needed. These include concrete, structural steel, paper machine bearings, oil and cooling water systems, electrical systems, rotating equipment, valves, and external machined surfaces.<\/span><\/p>\n
Strategies for Corrosion Protection<\/span><\/h2>\n
Some strategies can be applied to operational equipment while the majority are designed for successful preservation during shutdown. Structural remediation is valid for either time and includes concrete repair with MCI\u00ae<\/sup><\/span>\u00a0<\/span>repair mortars and surface applied corrosion inhibitors (SACIs), as well as rust removal on metal surfaces. Operational corrosion protection strategies include the use of VpCI\u00ae<\/sup><\/span>\u00a0<\/span>Emitters for electrical systems, corrosion inhibitors for cooling water and condensate systems, and VpCI<\/span>\u00ae <\/span><\/sup>aerosols for maintenance of valve fasteners and bushings. The shutdown and warehousing phases receive the most attention in this guide as Cortec\u2019s prime area of expertise. VpCI<\/span>\u00ae <\/span><\/sup>fogging fluids for turbine flow paths, oil additives for gearboxes, and CorrLube<\/span>\u2122 <\/span><\/sup>VpCI<\/span>\u00ae <\/span><\/sup>Lithium EP Grease for purging bearings are some of the key technologies and techniques outlined.<\/span><\/p>\n
Equipping Plant Owners<\/span><\/h2>\n
At any stage of a plant\u2019s life cycle, it is important for owners and managers in the pulp and paper industry to be equipped with a variety of ways to mitigate corrosion and maintain asset value. Cortec\u2019s new guide offers valuable answers, especially in the critical period of layup, that help decision-makers do so. Scroll down to read about \u201cCorrosion in the Pulp & Paper Industry.\u201d <\/span>Contact Cortec\u00ae<\/sup><\/span>\u00a0<\/span>for specific assistance<\/span><\/a>.<\/span><\/p>\n
Keywords: corrosion in the paper industry, Cortec layup guides, corrosion in pulp and paper plants, bearing layup, concrete repair, paper mill shutdown, VpCI, asset preservation, mitigate corrosion, corrosion risks on idle equipment<\/span> <\/em><\/strong><\/span><\/p>\n
Corrosion in the Pulp & Paper Industry<\/span><\/h2>\n
Pulp and paper mill sites consist of four major facilities:
\n\u2022 Mill
\n\u2022 Power plant and substation
\n\u2022 Warehouse
\n\u2022 Wastewater treatment plant<\/span><\/p>\nEach facility experiences corrosion due to the corrosive gases generated in the mill and the wastewater treatment plant. This document will concentrate
\non corrosion protection in the mill, warehouse, and wastewater treatment plant.<\/span>[1]<\/span><\/p>\nStudies performed by CC Technologies and published in March 2002 estimated the annual direct cost of corrosion in the pulp and paper industry to be $6.0 billion.<\/span>[2] <\/span>This cost did not include the costs related to revenue loss. Cost of corrosion is expected to increase as plants age and the experienced workforce decreases due to retirement and downsizing.<\/span><\/p>\n
There are two primary pulping methods used in the industry: mechanical and chemical. Chemical pulping is used approximately 90% of the time. The sulfate or kraft process is the primary chemical process comprising approximately 80% of the chemical pulping capacity.<\/span>[3] <\/span>One of the major drawbacks of chemical pulping is the corrosive gases and greenhouse gases generated in the process.<\/span><\/p>\n
Typical Corrosive Gases and Liquids:<\/span>[4]\n<\/span>\u2022 H<\/span>2<\/span><\/sub>SO<\/span>3 <\/span><\/sup>\u2013 Sulfurous acid
\n\u2022 H<\/span>2<\/span><\/sub>SO<\/span>4 <\/span><\/sub>\u2013 Sulfuric acid
\n\u2022 HNO<\/span>3 <\/span><\/sub>\u2013 Nitric acid
\n\u2022 Black liquor
\n\u2022 White liquor
\n\u2022 Green liquor
\n\u2022 Calcium bisulphite
\n\u2022 CaO \u2013 Calcium oxide
\n\u2022 NaOH \u2013 Sodium hydroxide
\n\u2022 Na<\/span>2<\/span><\/sub>CO<\/span>3 <\/span><\/sub>\u2013 Sodium carbonate
\n\u2022 CO<\/span>2 <\/span><\/sub>\u2013 Carbon dioxide
\n\u2022 H<\/span>2<\/span><\/sub>S \u2013 Hydrogen sulfide
\n\u2022 SO<\/span>2 <\/span><\/sub>\u2013 Sulfur dioxide<\/span><\/p>\nMost of the corrosive chemicals are found in areas of the plant where wood fibers are broken down or digested. The cooking liquors listed above (white, green, and black) all are very corrosive; contain potentially hazardous and\/or toxic ingredients; and corrode the pipes, valves, pumps, etc. with which they come in contact. Each system and component involved in the paper-making process is negatively impacted by the plant atmosphere.<\/span><\/p>\n
Papermaking Process<\/span><\/h2>\n
There are three major types of paper machines used in today\u2019s industry\u2014the Fourdrinier, twin-wire formers, and multi-ply formers\u2014of which the Fourdrinier is most prevalent.<\/span>[5] <\/span>Corrosive gases not only attack the equipment, but also the concrete and structural steel components of the plant infrastructure. Therefore, any corrosion prevention program should address the structures, equipment, and systems to minimize the total cost of corrosion to the plant. Cortec\u00ae<\/sup><\/span>\u00a0<\/span>Vapor phase Corrosion Inhibitors and Migrating Corrosion Inhibitors (MCI\u00ae<\/sup><\/span>) provide corrosion protection by displacing moisture (hydrophobic action) from the metal surface and neutralizing the surface electrical charge (ionic bonding). This eliminates free electrons\/protons that interact with corrosive elements, thus preventing initiation of corrosion cells. Cortec\u00ae<\/sup><\/span>\u00a0<\/span>products have been developed to optimize corrosion prevention in corrosive atmospheres such as those experienced in pulp and paper mills.<\/span><\/p>\n
BUILDINGS<\/span><\/h2>\n
Existing concrete should be inspected using GalvaPulse or iCorr corrosion measuring equipment to identify potential damage. Meaningful readings can be effectively accomplished using a grid network and statistical analysis. Once damage is identified, it can be repaired using Cortec<\/span>\u00ae <\/span>MCI<\/span>\u00ae <\/span>enhanced repair mortars and following the recommended repair procedure.<\/span><\/p>\n
Cortec\u00ae<\/sup><\/span>\u00a0<\/span>repair mortars \/ repair mortar additives include the following:
\n\u2022 <\/span>MCI\u00ae <\/sup>-2006 NS<\/span><\/a>
\n<\/span>\u2022 <\/span>MCI\u00ae<\/sup>-2023<\/span><\/a>
\n<\/span>\u2022 <\/span>MCI\u00ae<\/sup><\/span> Mini Grenades<\/span><\/a>
\n<\/span>\u2022 <\/span>MCI\u00ae<\/sup><\/span>-2039 <\/span><\/a>High Performance Horizontal Repair Mortar
\n\u2022 <\/span>MCI\u00ae<\/sup><\/span>-2040 <\/span><\/a>High Performance Vertical\/Overhead Repair Mortar<\/span><\/p>\nExisting concrete that is in sound condition can be protected using surface treatments such as the MCI\u00ae<\/sup><\/span>-2020 <\/span><\/a>Series and water-repellent\/weather-proofing sealers such as <\/span>MCI\u00ae<\/sup><\/span>-2018<\/span><\/a>, <\/span>MCI\u00ae<\/sup><\/span>2019<\/span><\/a>, <\/span>MCI\u00ae<\/sup><\/span>-2021<\/span><\/a>, and the <\/span>MCI\u00ae<\/sup><\/span>-2022 <\/span><\/a>Series. The inhibitors in these products migrate into the concrete over time to
\nprotect embedded rebar and wire mesh.<\/span><\/p>\nSTRUCTURAL STEEL<\/span><\/h2>\n
Situations like the one pictured occur when conventional coatings are scratched and\/or chipped, allowing moisture and corrosive gases to access the bare metal. Corrosion is a voluminous product and, as it grows, it puts pressure on the coating, eventually exceeding the coating bond strength, causing the coating to lift off the metal, and exposing additional surfaces to the corrosive atmosphere. As this reaction progresses, blisters appear, followed by bubbles and eventually sheets of coating peeling from the surface. Over time, this ultimately leads to failure of the structure unless proper action is taken. Conventional repair methods include mechanical cleaning, sand blasting, grinding, or wire brushing, followed by repainting with the same coating.<\/span><\/p>\n
Cortec\u00ae<\/sup><\/span>\u00a0<\/span>rust removers, cleaners, and coatings with corrosion inhibitors provide a more user-friendly, cost-effective process. The first step is to address existing corrosion. If sufficient metal cross-section remains to meet minimum design requirements, Cortec\u00ae<\/sup><\/span>\u00a0<\/span>rust removers <\/span>VpCI\u00ae<\/sup><\/span>-422<\/span>, <\/span><\/a>VpCI\u00ae<\/sup><\/span>-423<\/span><\/a>, or <\/span>VpCI\u00ae<\/sup><\/span>-426 <\/span><\/a>can be used to dissolve away the rust without mechanical cleaning. The metal should then be rinsed with an alkaline cleaner\/neutralizer such as <\/span>VpCI\u00ae<\/sup><\/span>-414<\/span><\/a>, <\/span>VpCI\u00ae<\/sup><\/span>-416<\/span><\/a>, or the <\/span>VpCI\u00ae<\/sup><\/span>-418 <\/span><\/a>Series. This process is good for small areas. <\/span><\/p>\n
For larger areas, it may be necessary to air blow or pressure wash the surface to remove loose particles and contaminants. Once clean, the surface can be coated with <\/span>CorrVerter\u00ae<\/sup><\/span>\u00a0<\/span>Rust Converter Primer<\/span><\/a>, which converts hematite into magnetite. The CorrVerter\u00ae<\/sup><\/span>\u00a0<\/span>is white when applied and turns black when fully cured. Multiple corrosion inhibitor coating systems are available as topcoats
\nover CorrVerter\u00ae<\/sup><\/span>.<\/span><\/p>\nThe pipe section in the photo shows one coating system where a rusty surface was conditioned for painting using the above-mentioned CorrVerter\u00ae<\/sup><\/span>\u00a0<\/span>