Hot-dip galvanized pipes are made by reacting the molten metal with the iron substrate to produce an alloy layer that combines the substrate with the coating. Hot-dip galvanizing is to pickle the steel pipe first. In order to remove the iron oxide from the surface of the steel pipe, the pickling is cleaned in a tank with ammonium chloride or zinc chloride aqueous solution or a mixture of ammonium chloride and zinc chloride in an aqueous solution and then sent to a high temperature – immersion plating tank. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion, and long service life. The substrate of the hot-dip galvanized steel pipe undergoes a complex physicochemical reaction with the molten plating solution to form a structurally dense, corrosion-resistant zinc-iron alloy layer. The alloy layer is integrated with the pure zinc layer and the steel pipe substrate, resulting in high corrosion resistance.
Cold galvanized pipes are electro-galvanized, and the amount of galvanization is very small, only 10-50g/m2, and their corrosion resistance is much worse than that of hot galvanized pipes. Most of the regular galvanized pipe manufacturers do not use electro galvanizing (cold galvanizing) in order to ensure quality. Only those small enterprises with small-scale and obsolete equipment use electro galvanizing, and of course, the price is relatively cheap. The Ministry of Construction has officially announced the elimination of technologically backward cold galvanized pipes, which shall not be used as water and gas pipes. The galvanized layer of cold galvanized steel pipe is electroplated, and the zinc layer is separated from the steel pipe matrix. The zinc layer is thin and the zinc layer simply adheres to the steel pipe substrate and peels off easily. Therefore, its corrosion resistance is poor. The use of cold galvanized steel pipes as water supply pipes is prohibited in new houses.
Galvanized pipes can use “two-component epoxy zinc yellow primer” as the primer, which must be painted by hand instead of roller coating. A thin layer is enough. Then spray the corresponding topcoat, for example, a coat of acrylic polyurethane paint can be sprayed on the surface, and the spray thickness is generally about 60 microns to achieve double protection. Phosphating treatment is required before painting: the surface of the galvanized pipe is passivated with phosphoric acid to improve the surface roughness and adhesion of the galvanized pipe. Before painting the galvanized pipe, it should be polished, and lightly polished, to avoid damaging the anti-corrosion layer of the galvanized pipe itself and remove the dirt on the galvanized pipe.
Galvanized pipes are used as water pipes. After a few years of use, a large amount of rust is generated in the pipes. The yellow water that flows out not only contaminates sanitary ware but also contains bacteria that breed on the uneven inner wall. Rust causes excessive levels of heavy metals in water, which is a serious health hazard. In the 1960s and 1970s, new types of pipes were developed and galvanized pipes were gradually banned in developed countries around the world. Four ministries and commissions including the Ministry of Construction of China also issued a document clarifying that galvanized pipes have been banned since 2000. At present, galvanized pipes are rarely used for cold water pipes in newly built communities, and galvanized pipes are used for hot water pipes in some communities.
Hot-dip galvanized pipe: The molten metal reacts with the iron substrate to produce an alloy layer, which combines the substrate with the coating. Hot-dip galvanizing is to pickle the steel pipe first. To remove the iron oxide from the surface of the steel pipe, the pickling is cleaned in a bath of ammonium chloride or zinc chloride aqueous solution or a mixture of ammonium chloride and zinc chloride aqueous solution and then sent to a hot-dip galvanizing bath. Hot-dip galvanizing has the advantages of uniform plating, strong adhesion, and long service life. The hot-dip galvanized steel pipe substrate reacts with the molten plating bath in a complex physical-chemical counter-galvanized steel pipe to form a structurally dense, corrosion-resistant zinc-iron alloy layer. The alloy layer is fused with the pure zinc layer and the steel pipe substrate. Therefore, its corrosion resistance is strong.
Galvanized seamless steel pipe: The amount of galvanization is very small, only 10-50g/m2, and its corrosion resistance is much different from that of hot-dip galvanized pipe. Regular galvanized pipe manufacturers can use cold galvanized pipes as water and gas pipes. The galvanized layer of cold galvanized steel pipe is electroplated, and the zinc layer is independent of the steel pipe substrate layering. The zinc layer is thin, and the zinc layer simply adheres to the steel pipe matrix and peels off easily. Therefore, its corrosion resistance is poor. The use of cold galvanized steel pipe as water supply pipe is prohibited in new houses.
Galvanized steel pipes are divided into cold galvanized steel pipes and hot galvanized steel pipes. Nowadays, galvanized steel pipes are widely used. Besides common high-pressure fluid pipelines such as water, natural gas, and oil, they are also used in the coal and oil industry, especially oil well pipelines in offshore oil fields. Condensation cooler, distillation coal for an oil pipeline, bridge pile, mine pipeline support pipe, etc. Galvanized steel pipes improve the corrosion resistance of steel pipes and extend their service life.
Used as a water pipe, a small amount of rust will appear after a few years of use. It not only infects sanitary ware but also contains a fungus that grows on the uneven inner wall. Rusting can lead to high levels of heavy metals in the water.
Hot-dip galvanized pipe melts the molten metal and iron alloy layer so that the substrate and coating induct each other. Hot-dip galvanizing is the process of immersing the steel pipe in acid. To remove iron oxide from the surface of the steel pipe, the steel pipe is pickled, mixed with an aqueous solution of ammonium chloride or zinc chloride, and then placed in a hot-dip galvanizing bath. The hot-dip galvanized coating has a uniform distribution, strong adhesion, and long service life. The substrate of the hot-dip galvanized steel pipe undergoes a complex physicochemical reaction with the hot-dip galvanizing bath, forming a dense corrosion-resistant zinc-iron alloy layer, alloy layer, and pure zinc layer, and steel pipe substrate fused together, so it is extremely corrosion resistant. To ensure quality, most conventional galvanized pipe manufacturers do not electro galvanize (cold galvanizing). Cold galvanized pipes are electro-galvanized with very little galvanization. Its corrosion resistance is very different from that of hot-dip galvanized pipes. . Those small enterprises with small scale and old equipment will use electro-galvanizing because the price is relatively cheap. The galvanized layer of cold galvanized steel pipe is an electroplated layer. The zinc layer is independent of the steel pipe substrate layer pressure. The zinc layer is very thin and easily adheres. Put on the steel pipe, it is easy to fall off. Therefore, cold galvanized steel pipe is prohibited to be used as water supply pipe for buildings because of its corrosion resistance.
(1) First, clean the steel surface with solvent to remove surface organic matter.
(2) Then remove loose or tilted oxidation, rust, weld slag, etc., with tools for rust removal (wire brush).
(3) Use pickling.
Galvanizing is divided into hot-dip galvanizing and cold-dip galvanizing. Hot-dip galvanizing is not easy to rust, while cold-dip galvanizing is more prone to rust.
Galvanized parts are non-ferrous metals, and non-ferrous metals have poorer adhesion than all ferrous metals. The commonly used alkyd iron red primer and epoxy iron red primer are not suitable for galvanized parts, otherwise, they will easily fall off. Alkyd paint is used on galvanized parts, saponification reaction will occur, not only the coating fails, but the original galvanized layer will also be damaged. The substrates suitable for galvanized parts are epoxy zinc yellow primer and epoxy ester zinc yellow primer.
Pay attention to when painting galvanized parts:
（1） If possible, you can phosphate the galvanized parts, or spray a thin layer of phosphate primer first.
（2） Sweep the surface of smooth galvanized parts.
（3） Wipe the surface of galvanized workpieces and galvanized pipes with solvent to remove the protective layer of crude oil and increase cleanliness.
（1） When you go to the mall to buy galvanized steel pipes, you need to take a correct look at the price of galvanized steel pipes. Look at several companies for comparison. At the same time, you also need to know that the more expensive the product, the better the quality. The brand, specifications, and specifications of the product have a lot to do with it. If you don’t understand it personally, it’s best to go with friends who know how to do it.
（2） When comparing the prices of galvanized pipes, it is necessary to choose several products of the same type for price comparison, so as to determine which one is more suitable for your choice. Furthermore, the characteristics of galvanized steel pipes and the purchasing skills must also be mastered, so that you can effectively prevent fraud by merchants and ensure personal interests.
（3） For the specifications that you need to use, you must be clear from the beginning. If you buy materials that do not match the actual material, it will seriously affect the normal use in the later period. If you are looking for the specifications you want, you need to make it clear to the merchant and record it in the contract.
(1) Difference in the manufacturing process: Galvanized steel pipe and non-galvanized steel pipe are the two major types of steel pipes. Galvanized means that the surface of the steel pipe is galvanized, while non-galvanized steel pipes are not.
(2) Difference in durability: Galvanized steel pipes are more resistant to corrosion, while non-galvanized steel pipes can withstand higher pressures. Galvanized steel pipes are less likely to rust due to the protection of zinc. Galvanized steel pipes are lighter than ordinary steel pipes.
(3) Difference in use: Galvanized steel pipes are generally used for making fences, fences, guardrails, and balcony railings. It is widely used in municipal projects, roads, factories, schools, development zones, gardens, squares, communities, and other places. Non-galvanized steel pipes are now basically replaced by galvanized steel pipes.
Defects in galvanized pipes can manifest in multiple ways. The mounting build-up of mineral deposits resulting from corrosion can obstruct water pressure. Low water pressure around the house is usually a sign of a massive build-up of mineral deposits in galvanized pipes.
A total replacement of the pipes is usually the only viable solution. In some cases, the obstructed pressure might result in uneven water distribution. This is typically the result of an uneven build-up of deposits across different portions of the pipes.
Besides obstructing water pressure, the mineral build-up can also contaminate the water. They can give rise to discoloration in the water. Sometimes, discolored water from rusty galvanized pipes can leave visible brown stains on a porcelain sink. And as the corrosion eats deeper into the pipes, it weakens their integrity, inducing leakages across them.
If any part of the galvanized pipes in an old house is leaking, then you should brace up for other leakage spots that could break forth owing to years of gradual corrosion.
It can be quite dicey to manage aging galvanizing piping as more and more problems might surface now and then due to continuous corrosion. Replacing an entire system of old galvanized pipes with modern piping like copper pipes or PEX might be expensive upfront, but the cost of repairing the old system might quickly outstrip this upfront cost over time.
To boot, leakages from compromised water pipes can damage many other parts of the house, causing issues like concrete leakages, mold build-up, cracks in walls, and damages to furniture, electronics, etc. And if the leakages are hidden from plain sight, they might go unnoticed for a long time, wasting hundreds or even thousands of gallons of water per year and causing mysterious increments in water bills.
Even if the galvanized pipes may seem to be in good condition in an old house, you’re inspecting, and you might run into perpetual repairs shortly after moving in if the pipe is in the final stretch of its lifespan.
Reach out to us today to get professional advice on how best to handle your galvanized piping issues. We are based in Southern California and provide service in the cities of Corona, Riverside, Redlands, San Bernardino, Highland, Eastvale, Chino, Ontario, and Rancho Cucamonga.
The short answer is yes, you should definitely look into an upgrade if your home is outfitted with galvanized pipes. Replacing your old pipes with new copper pipes might be an expensive job, but it can save you a ton of money in the long run. However, if your pipes seem to be in a good state currently and you aren’t planning on living in your home for several decades, you might be fine with just a little minor maintenance.
The first thing you have to consider is money saved on future repairs. Since we know that galvanized pipes break down over time, replacing them can significantly lower your chances of expensive leaks, pipe bursts, and water damage.
Water damage that builds up over time can lead to some serious repair bills. And the small, undetected leaks that cause invisible water damage also waste hundreds, even thousands of gallons of water every year, costing you even more on your utility bills.
Although galvanized pipes have a general life expectancy of 50 years, their lifespan depends on many factors, from the frequency of use to the amount of water pressure. As such, they might come in need of replacement sooner or later than expected. In the plumbing industry, a replacement is called a recipe. When you repipe a house all the existing hot and cold water lines get replaced usually in PEX Uponor.
If they’ve been well maintained and have not been subjected to excessive pressure, then you might be able to get a few more years from their backstretch. Frequent exposure to extreme pressure, on the other hand, not only weakens the pipes but also accelerates corrosion, detracting from the lifespan of the pipes in more ways than one.