For many welders, quality is a definite requirement in their various welding projects. From small minor to major welding projects, welders have numerous techniques of checking their output; one of them is testing the cross sections of their weld. To perform this type of testing accurately, welders make use of a process called acid etching to determine the arrangement of metal when they weld various metal alloys together. This process determines the smoothness and fineness of the metal alloys as they mix together via welding. Acid etching a cross section of a weld is an art and there are many techniques that can be utilized. Let us get started.
Purpose of Acid Etching Cross Sections.
The purpose of acid etching is for quality control. Welders use this process to spot and determine any defects in the metals that they weld together. Defects such as poor fusion and porosity can be detected by the naked eye and they represent poor quality of work that welders dare not produce for their projects. This is especially true when there are clients involved who hire welders to perform masterful welding jobs in repair, maintenance, customization, and many more welding projects.
How Welders Perform Acid Etching.
When welders perform acid etching to test their cross section welds, they begin this process by extracting a sample from the newly welded joint. This process is known as cold cutting, which requires welders to use a tool such as a bandsaw to extract a sample. Next, they must clean the sample of all burn marks and corrosion by continuously polishing the sample with emery solution. Once the sample has been polished properly to the point that it has obtained a smooth and even polish, welders can now perform the process of acid etching, which occurs in these steps:
Once the sample is ready, welders apply a solution made of acid on a clean cloth which they gently wipe on the sample’s surface continuously until the weld marks and corrosion disappear. The acid used for the solution is usually nitric acid that is mixed with water. The ratio of acid to water is usually 90:1 because nitric acid works ideally to clean various metal alloys of corrosion and weld marks after each welding process. Since not all metal alloys react accordingly to nitric acid, there are occasions wherein welders must apply the solution over and over again until the sample discolors itself of corrosion and weld mars.
After the sample has obtained clear visibility, it will reveal different features as various metal alloys have different chemical reactions to nitric oxide. Here, a welder will determine the distinct color differences of the joined alloys, as well as the actual welded metal and the parent metal in the surrounding areas of the sample. This is how acid etching is basically achieved.
Various Acids Used for Etching.
When it comes to acid etching, there are other acids that are utilized aside from nitric acid because various metal alloys reveal different features and reactions to acid etching after a welding procedure is conducted. For this reason, welder must use a number of acids that include:
- Nitric Acid. This acid is the most popular solution to use in acid etching as it is suitable for a variety of metal alloys such as silver and lead. Some welders even mix nitric acid with salt because it works to clear metal of corrosion and weld marks that come after welding. Nitric acid with salt mixture even works impressively for welders looking to design their metal with specific art and logos.
- Hydrofluoric Acid. Another popular acid utilized for acid etching is Hydrofluoric Acid as welders use this whenever they work with glass, ceramics, and cast iron to name a few. Hydrofluoric Acid is mostly used for metal art purposes where welders add logos, art designs, and lettering to various projects such as scrap metal art.
- Sulphuric Acid. Sulphuric Acid solution for acid etching is a rather strong solution that is capable of removing steel from copper in a cross welding. Sometimes fusing metal alloys can be a difficult process especially when welding steel and copper because the fusion of metal often makes it impossible for welders to determine any defects in the weld. This is when they must utilize Sulphuric Acid as it can produce deep lines that are visible to the naked eye.
- Hydrochloric Acid. Another strong acid etching solution that welders use is Hydrochloric Acid. Hydrochloric Acid is an extremely corrosive acid that is normally used for etchings on zinc and steel.
Advantages of Using Acid Etching for Welding Cross Sections.
There are numerous advantages that welders have when they use acid etching in welding cross sections. As previously stated, acid etching is a technique of testing the strength of a particular cross weld. It is a manner of testing structure and quality of metal alloys that ensure the welding will last. It also provides welders with a clear appearance of the internal structure of a weld. Other advantages of acid etching a cross section are:
- It allows welders to detect welding problems such as depth of root penetration, lack of fusion, corrosion, cracking, and many more. These are major problems for any welding job because they severely compromise the quality of a cross section weld.
- When welders utilize this technique continuously, their skill as a welder improves substantially because they gain experience with working with numerous metal alloys. From this experience, they avoid producing subpar welding jobs.
- It allows welders to utilize numerous acid solutions that are suitable to the metal alloys that they work with.
- Acid etching is a very simple yet effective technique that all welders can utilize for quality control in their welding projects. This will keep their customers returning to them for additional welding projects.
- It aids welders in correcting poorly performed pre-welded procedures.
- It streamlines the entire welding procedure to produce efficient and satisfactory results.