The ASTM A500 and the CSA G40.21 are two popular specifications in mechanical usage. In this blog, we will be taking a look at the differences between the two. 


The ASTM A500 is a standard specification for seamless carbon steel structural and cold-formed welded tubing. It is provided by the American Society for Testing and Materials (ASTM), which has also sanctioned round, square and rectangular shapes for the specification. 

The A500 is made up of carbon, manganese, phosphorus, sulfur, and copper. The composition of the different chemicals present in the alloy changes with the different grades. It is the most common specification used in North America for Hollow Structural Sections (HSS). 

Square high carbon metal tube background for heavy industry.
Square high carbon metal tube background for heavy industry. Source: Depositphotos

Different Grades of the ASTM A500 

Based on different properties like tensile strength, heat treatment and chemical composition, there are four grades of the A500 - Grade A, B, C and D. 

Here are the different properties of the varying A500 grades: 

Grade A:

Tensile Strength:       45,000 psi (min)

Yield Strength:          39,000 psi (min)

Elongation:               25% 

Grade B:

Tensile Strength:       58,000 psi (min)

Yield Strength:          46,000 psi (min)

Elongation:               23%

Grade C:

Tensile Strength:       62,000 psi (min)

Yield Strength:          50,000 psi (min)

Elongation:               21%

Grade D:

Tensile Strength:       58,000 psi (min)

Yield Strength:          36,000 psi (min)

Elongation:               23%

It is worth noting that the yield strengths of the square and rectangular shapes are higher than the round ones. In terms of chemical composition, the requirements for Grade A, B and D are the same. However, Grade C differs in terms of the amount of carbon % by weight in heat. 

While the other three grades need 0.26 percent, Grade C requires 0.23 percent of carbon. The other materials remain the same for the pipe. And in case of all the grades, the minimum amount of copper remains optional. 

A key point to note is that Grade D pipes must be heat treated in order to comply with the specifications.

Use Cases of the A500 Pipe 

Here are some of the situations in which you may come across an A500 pipe: 

  • Building columns 
  • Communication towers 
  • Oil field services 
  • Highway columns 
  • Structural supports 

While round pipes are also used in the transportation of materials like petrol or natural gases. As a result, the round versions find usage in refineries, petrochemicals and boiler equipment. 

On the other hand, due to the good torsional and bending strength of the square versions - the square and rectangular versions find use in the design of mechanical parts. 

Specifications of the A500 to Note 

The ASTM A500 can be designed in either seamless or welded configuration. While the seamless pipes possess higher load-bearing and strength capacities, the welded pipes are cheaper on the market. 

In order to avoid cracking, it is vital that the pipes are preheated before they are welded. 

Based on the situation, there are a number of surface protection coatings that can be used. Namely: hot dip galvanized, varnish/oil coating, pre-galvanized, uncoated (black). 

CSA G40.21 

The Canadian equivalent of the ASTM A500, the CSA G40.21 is mainly used in plates, 

shapes, hollow sections, sheet, sheet piling, 

cold-formed channels and bars used in construction. While the ASTM sanctions the specifications for the A500, the CSA (Canadian Standards Association) does so fro the G40.21.

The resistance level of the CSA G40.21 ranges from 50W to 350W. But, it can also be extended up to 480W if necessary. 

Differences Between CSA G40.21 and ASTM A500 

The two specifications of piping are similar in a lot of ways. However, there are a few significant differences to take note of. The specifications for the CSA G40.21 are much more strict due to their usage in Canada. 

The tensile strength for the G40.21 is capped at 90,000 PSI while the A500 simply has a lower limit of 62,000. Also, the elongation percentage is a minimum of 22 in the Canadian version, while ASTM prescribes a 21% minimum. There are also minor differences in tolerance between the two. 

The American standard is preferred during international usage, while authorities in Canada prefer using the Canadian standards implemented by the CSA. In terms of chemical properties at the very least, there is an overlap between the two standards which can be used to fashion a doubly compliant product. 

Physical properties like tensile strength and elongation percentage have only a slight difference. On that front, there will be subtle differences that will reflect while testing. 


Based on the two sets of specifications provided, there is a subtle difference in terms of composition and mechanical properties of the two pipes. But, they can be constructed to the same configurations which can help them stay compliant in both situations.