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Understanding and Preventing Fastener Corrosion

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fastener-corrosion

Fastener failures occur when the wrong fasteners are being used for a project, or the right fasteners are being treated incorrectly. Fastener corrosion is one of the most prevalent issues causing fastener failure. Let’s go over the what corrosion is, types of corrosion and how to avoid it in your project.

How Fastener Corrosion Occurs

Corrosion is the destructive alteration of metal by chemical or electrochemical reactions within its environment. Corroded parts fail for a variety of reasons including:

  • Loss of mechanical integrity: corroded areas do not possess mechanical strength
  • Fatigue: Corrosion site causes cracks in the fastener
  • Loss of surrounding clamped materials: the material the fastener is clamping erodes around the head of the fastener
  • Stress corrosion: exposure to harsh environment causing embrittlement

Types of Fastener Corrosion

There are two main categories of fastener corrosion: a direct chemical attack or electrochemical corrosion. 

A direct chemical attack occurs when the material the fastener is made out of is soluble in its environment. This typically happens in harsh environments, like the oil and gas industry. To prevent this, make sure to choose a fastener material that is unaffected by solvent, or choose the proper coating to withstand the solvent. 

Electrochemical corrosion encompasses many types of corrosion, and it results in many small electrical current flows through the fastener. This process results from the contact of two different types of metal or the presence of atmospheric oxygen within the presence of an electrolyte. Here are a few types of electrochemical corrosion you may encounter:

  • Galvanic Corrosion - caused when two different metals are in contact, resulting in pitting or erosion damage.
  • Stress Corrosion Cracking - caused when tensile stressed parts are in a corrosive environment. There is too much tension on the fastener, making it more susceptible to failure. Stress corrosion cracking can happen much more quickly than the other types of corrosion.
  • Crevice corrosion - occurs in the crevices of a fastener that isn’t properly ventilated. This happens any place dirt or moisture accumulate. This is one of the more dangerous types of corrosion, as it often isn’t caught until after the damage has occurred.
  • Uniform corrosion - occurs due to improper coating of the fastener, causing rust that makes the fastener difficult to replace.
  • Pitting corrosion - caused when microscopic holes form on the fastener. 

Avoiding Fastener Corrosion

The best way to avoid corrosion is to ensure you are using the right materials and coatings for the job. You should also make sure the fasteners are being stored properly on the jobsite, and are installed correctly. If you have any questions, always refer to your project engineer and follow the proper standards for the project.

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Looking for domestic and imported fasteners? Birmingham Fastener has you covered! Our massive inventory ensures your bolts will be shipped fast and on time! Call us or get a quote online today!

Waterworks Fastener Standards: AWWA, ASTM, and ASME

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waterworks-awwa

Waterworks Fastener Standards

When we talk about the specifications on our waterworks products, we often reference the waterworks fastener standards from the ASTM, AWWA, and ASME. These organizations provide the standards over many things including all fasteners used in waterworks applications. It’s important to keep up with these organizations to ensure that all standards are being followed. Here’s an overview of the organizations and their responsibilities.

American Water Works Association (AWWA)

The American Water Works Association (AWWA) is an international non-profit association founded to manage water quality and supply. It is the largest organization of water supply professionals in the world, including scientists, public water and waste system professionals, manufacturing companies, regulators, environmentalists, and others working to improve water systems around the world. The AWWA develops industry standards for products and processes related to water. There are over 150 AWWA standards covering filtration systems, utility management practices, pumps, tanks, steel, pipes, and fittings. At Birmingham Fastener, we follow AWWA standards for all of our water works products including t-head bolts, mechanical joint gasket and bolt packs, and other products. To learn more about the AWWA, visit their website.

ASTM International

ASTM International is an all-encompassing organization that produces over 12,000 standards for many different types of products globally. In relation to structural bolt specification, the ASTM provides the standards for how the bolts are made and what raw materials can be used to create them. Each ASTM standard is reviewed at a minimum of every three years, meaning standards can change. For example, prior to 2015, ASTM A325 and A490 were separate specifications. After a review of the standards, these were replaced by F3125, making A325 and A490 grades under the F3125 specification. ASTM International also provides the standards on testing methods and what tests have to be done on all structural bolts prior to installation. To learn more about ASTM International, visit their website.

ASME

The American Society of Mechanical Engineers (ASME) is a not-for-profit organization that works towards collaboration and skill development for engineering disciplines. They produce codes and standards for many different technical fields, including the fastener field. In regards to fasteners, the ASME provides manufacturers with dimensional standards and thread lengths for all types of bolts, including bolts used in waterworks. For more information on the ASME, visit their website.

Mechanical Joint T-Head Bolt Technical Information

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This chart aligns with ANSI/AWWA C111/A21/11-00. If you have any questions about this chart or our products, please contact our sales team.

*Size and length are in inches. Torque is in foot-pounds.

Nominal
Recommended
Pipe Size 		Quantity Size Length Torque
3 4 5/8 3 45-60
4 4 3/4 3 1/2 75-90
6 6 3/4 3 1/2 75-90
8 8 3/4 4 75-90
10 8 3/4 4 75-90
12 8 3/4 4 75-90
14 10 3/4 4 1/2 75-90
16 12 3/4 4 1/2 75-90
18 12 3/4 4 1/2 75-90
20 14 3/4 4 1/2 75-90
24 16 3/4 5 75-90
30 20 1 6 100-120
36 24 1 6 100-120
42 28 1 1/4 6 1/2 120-150
48 32 1 1/4 6 1/2 120-150