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Pipe Corrosion – Causes and Prevention Techniques

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Metal pipes are essential in our day-to-day lives and in industry for transporting and distributing liquids (e.g., oil, water etc.) from one point to the other. When corrosion takes place, the impacted pipe starts disintegrating and the distribution of liquids is impacted. For pipes transporting water, corrosion may also impact the color, taste, and odor of water. This may be harmful in cases where the water is meant for human consumption. Along with the pipe itself, pipe fabrication connections are seriously impacted by corrosion. So, what are the causes of corrosion and how can it be prevented? This blog will look to discuss this interesting topic going forward.

Causes of Pipe Corrosion

  • Acidity and Alkalinity – Acidity is one of the factors that cause corrosion in metal pipes. Water has a low PH if it is untreated because of the presence of carbonic acid or other acids. The presence of these acids in water causes corrosion as they will react with pipes. This reaction will go on for a while and eventually the pipes get corroded. Alkalinity refers to bases which are contained in water. These bases are not good for pipes since they are anti-corrosive.
  • Electric Current – It is well known that most of the water pipes are underground. Hence, the electric current will come from earthing. The excess electricity is damped to the ground to prevent accidents in electrical appliances. This electric current that goes to the ground will cause corrosion in these pipes.
  • Material and Organic Constituents – Water contains minerals and organic constituents. These dissolved minerals have a great chance of causing corrosion in pipes if they are not eliminated. For instance, dissolved oxygen in water facilitates corrosion in pipes. The only way to eliminate the minerals and organic constituents in water is by treating that water before entering the pipes.

Prevention of Pipe Corrosion

  • Cathodic Prevention – Cathodic protection is the use of electrical current to prevent corrosion. This is done by connecting the pipe to the negative pole of a DC generator or the anode metals like magnesium so the entire pipe acts as a cathode. The cathodic protection method is very effective for metal pipes that are buried. When the pipe is made to be a cathode, then this will greatly prevent corrosion simply because corrosion only occurs at the anode and not the cathode since corrosion is an electrochemical process.
  • Proper Pipe Material – The type of pipe material used for welding pipes also has a great influence on preventing corrosion. There are pipe materials that are resistant to corrosion, these kinds of pipe materials will do a great job of preventing corrosion. The best pipe materials that one should consider using are the alloys of iron or steel with chromium, copper, or nickel. They are quite expensive, but they are the best pipe materials for prevention of corrosion and also helps in reducing scrap during the pipe manufacturing process.
  • Water Treatment – Water treatment involves adjusting the pH value. The moment the PH value is low or high that will facilitate the corrosion of the pipes. So, the water must be treated and the PH should be between 6.5 to 8.5, this is the PH that will prevent the pipes from corroding. Also, treating water tends to take control of calcium carbonate which increases the alkalinity of water. Removal of oxygen from water also aids in the prevention of corrosion in metal pipes, since oxygen is one of the factors that increase corrosion in pipes. The addition of sodium silicate in water when treating it also prevents corrosion in pipes.

The Last Word

It is important to note that corrosion of pipes cannot be eliminated since oxygen will always be available unless the earth is filled with inert gases. However, corrosion needs to be managed to the maximum extent possible else it will impact pipes in the long run and replacement of pipes will be an additional expense. Thus, pipe corrosion is an ongoing phenomenon and the management of corrosion by heavy steel fabrication companies needs to be an ongoing practice as well!

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Process of Welding Pipes

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During his career, a metal fabricator will be expected to work on a wide range of jobs, using various metals of different thicknesses. Joining curved pieces of metal is more difficult than welding flat sheets, so by far, the most challenging process one is likely to come across is pipe welding, where it will be required to join cylindrical metal tubes using either SMAW or gas shielded arc welding processes involving pressure vessels. The pipe welding positions and techniques are often quite uncomfortable, especially if the pipe is fixed and access is restricted. As a result, learning the structural welding basics will give one a much better understanding of TIG and MIG welding in general, which is a great foundation for more complex procedures. This blog will explore this topic in further detail.

How to Weld Pipes – Basis Guide and Process

If a welding joint does not use a tacked backing plate, it’s known as open root welding, which is the most common process used while pipe welding. This is particularly difficult because one will essentially be welding across a gap (albeit a small one) so it’s important to use the right technique so that one does not make a mess of the whole job. Every welder will have a ‘good’ side and a ‘bad’ side when it comes to welding, depending on whether they’re left- or right-handed. For right-handed welders the left-hand side of the pipe is the challenge; for left-handed welders, it’s the right-hand side of the pipe which is the most difficult. Anticipating this obstacle and learning how to overcome it is the best way to ensure super strong, neat welds every time.

Pipe fabrication, and specifically welding, often uses quite thick, heavy-duty materials, and the open root nature of the welds means that penetration can be poor if not done properly. Leaving poorly penetrated welds on tough, industrial pipe welding jobs can be disastrous. It will need to be ensure that full penetration is achieved, however since that it’s unlikely that welding can be done from the inside of the pipe as well as the outside, one can combat this potential problem by using a groove weld.

Testing Pipe Welding

Inspecting the weld visually is one such method, which is by far the cheapest, quickest and easiest. It involves nothing more than looking at the weld to discern its quality, which can be a very subjective process. It can’t be used as a reliable method for detecting internal weld  defects, so this method is mainly used when poor quality welds won’t put anyone or anything in danger.

Liquid dye penetrant testing is the second method, where a dye is sprayed or brushed onto the surface of the metal. The dye will highlight any surface cracks or imperfections which aren’t visible to the naked eye, making it more effective than a visual inspection, although the cost of the dye does mean that it’s marginally more expensive.

X-ray testing is the only really practical method of detecting internal weld defects, which is why it’s used on jobs where the quality of the weld is important for safety reasons. It works in a very similar way to X-rays which we have on the human body to look at broken bones, except on a much grander, more industrial scale. As a result, there are some risks associated with this method, so it should only be carried out by trained professionals. These three methods are called non-destructive testing (NDT), where the welds must remain intact. It may be appropriate to actually break apart the pipe weld by separating it into sections and testing the strength and quality of each one.

Conclusion

Mastering the art of pipe welding will take one’s welding career far beyond the potential of hobby or ordinary flat plate welding. The welder will learn some of the most challenging welding techniques in the industry, but will also gain a highly prized skill set which is desired by employers and which will probably lead to a higher salary. One won’t need any extra special equipment, but this isn’t a welding process for the half-hearted!

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Three Metal Fabrication Stocks to Watch Out For

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The demand for metal fabrication faced a major challenge when it was badly hit during the COVID-19 pandemic, and even now the industry has been witnessing deceleration in demand of late due to muted customer spending. There are other headwinds as well, such as a labor crisis, coupled with the ongoing supply-chain issues and persistent shortages of critical materials. While these factors are affecting the fabrication industry’s production output, certain industry players are expected to gain from their cost-management efforts, focus on improving efficiency and investment in automation. This blog will cover three fabrication stocks in this regard and will try to identify what makes these companies stand out from other metal fabrication stocks.

The Timken Company

The company continues to witness new business wins in new markets and regions. Its diversity in terms of end market, customer and geography, product innovation and engineering expertise provides it with a competitive edge. Underlying customer demand and end-market momentum remain strong across most of its sectors. Apart from strong demand, earnings growth will be supported by benefits from price realization, growth initiatives and operational excellence initiatives. Timken continues to pursue strategic acquisitions to broaden its portfolio and capabilities across diverse markets, focusing on bearings and pressure vessels, adjacent power transmission products, and related services. It recently inked a deal to acquire GGB Bearing, which boasts a portfolio of metal-polymer bearings, serving a wide range of industries. This acquisition provides strong synergies and expands Timken’s business by adding products with solid growth outlook.

Norsk Hydro ASA

Higher all-in metal and alumina prices, and record high results in Extrusions contributed to Norsk’s solid results during 2022. Norsk has been adjusting capacity to meet market demand, and continues focusing on reducing costs and improving operational excellence, which will help drive margins. It continued to progress on its Hydro 2025 strategy in the fourth quarter of 2022, both strengthening its position in low-carbon aluminum and growing in the new energy areas. Greener aluminum with a lower carbon footprint is necessary with aluminium tariffs being levied on carbon emissions. In the first quarter of 2023, Norsk’s sales were 45% higher year over year, supporting its target to double the sales of greener products by 2025. Extrusions remain a key growth area in NHYDY’s 2025 strategy and in the third quarter of 2022, it decided to invest in 12,000 tons of additional capacity at its extrusions plant in Rackwitz, Germany.

Northwest Pipe Company

Northwest’s Engineered Steel Pressure Pipe business has been witnessing solid bidding and a strong backlog for a while which bodes well for the segment. The Precast business continues to perform well and its pipe spool fabrication order levels are expected to grow in the near term, leading to further margin expansion, backed by a robust precast market. Rising demand for developed water sources and the pressing need to upgrade, repair and replace the aging U.S water and wastewater systems present a huge opportunity for Northwest. Backed by a strong balance sheet and solid liquidity, Northwest continues executing its growth strategy. In October 2021, it acquired ParkUSA, a precast concrete and steel fabrication-based company that develops and manufactures water, wastewater, and environmental solutions. This marked Northwest’s third major transaction in just more than three years. The ParkUSA integration remains on schedule and is steadily contributing to the Precast segment’s performance.

Closing Call

An interesting observation from the analyses of the three stocks is that there is no single contributor to their rising potential. While Timken has benefited from strategic acquisitions, Norsk has focused on green energy areas and Northwest has a robust steel pipe business which is driving growth. Thus, in the challenging metal fabrication world, it is important to focus on one’s strengths while managing macro and micro economic headwinds – important lessons for other fabrication companies!

© K999 Engineering & Construction Co. Ltd. 2023