To Welding Inspectors, acid etching kits are just another tool. That box of cushioned vials fits snugly in with an extensive range of joint examining instruments. True, these substances are a lot more energetic than a dye penetrant. Acids are designed to be corrosive, after all. But these aren’t any old volatile chemicals. On the contrary, they’re specially formulated so that they’ll dissolve boundary obscuring slag inclusions.
It’s a Defect Clarifying Mechanism
Acid etch examinations dissolve weld slag. The test emphasizes the boundaries between welds and base metal edges. In other words, the test emphasizes the topographical anatomy of a weld. Otherwise, the anticipated demarcation zones around each weld section would be impossible to make out. Unlike the age revealing rings inside a felled tree, those boundary lines aren’t instantly recognizable, not unless a weld is treated with an acid etching solution. However, like that tree, this inward-looking perspective can’t be viewed until a weld cross-section is taken. Polished and acid-etched, the sliced away transverse section is prepped so that it’ll reveal its secrets.
A Destructive and Corrosive Weld Examining Ordeal
No doubt, the examination process can only be described as an ordeal. After an inspectors’ cushioned examination box opens up, a hydrochloric or nitric acid solution is cautiously applied. The test cross-sectional sample has been cut away from a suspect weld, and now it’s sitting in a dish full of acid. The corrosive compound eats its way into the sample. Soon after, a very revealing chemical action takes place. Weld-to-base metal boundaries are highlighted, slag inclusion deposits dissolve, hidden gas pockets are exposed, and all once masked weld defects become much easier to recognize.
Employed as a Soundness Determining Device
Weld integrity is severely tested by this destructive joint torturing regimen. With slag inclusion melted away, weld defects stand exposed. If a weld boundary can be highlighted in this manner, think how cracks will come to light. Porosity issues, poor fusion difficulties, hairline fractures and all other forms of fusion degradation, they can’t hide from a chemical attack that’s designed to dissolve all opportunistic flaw-masking weld detritus.
If a weld defect is buried deep inside the cooled metal, it’s nigh-on impossible to spot that flaw. Even dyes and microscopes can miss tiny porosity blemishes and other welder or equipment applied imperfections. Once missed, the flaws worsen over time, a weld causes a structural flaw to appear, and a construct suffers. Weld Inspectors can’t abide such quality and safety impacting matters, which is why an acid etch test examinations is so important. Used to destructively bring out concealed joint defects, the corrosive substance exposes the tiniest weld discontinuities for all to see.