Nital Surface Etchants

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Macro Examination of Carbon Steel Welds: The surface is abraded by the use of various grades of Silicon Carbide papers then washed clean. A small amount of the etchant is applied to a cotton pad then wiped across the surface to be examined. The longer the etchant is in contact with the metal the more defined the weld structure will appear. Rinse with water to remove the etchant and stop the reaction.

Nital Micro Etchants: Nital Etch Inspection (sometimes referred to as “Temper Etch”) is a non-destructive testing technique used to evaluate the effects of manufacturing processes such as machining, grinding and heat treatment on metallic components. Under certain circumstances machining and grinding can introduce sufficient heat into a component to heat-treat its surface. This is generally caused by local over-heating and can produce undesirable changes in material properties.

Using a Nitric acid solution, machined components are etched revealing grinding and machining abuse. The nital acid etchants work by forming a colored surface film on the steel and attacking its surface to form pits.

The etched surface is then microscopically examined to detect detrimental microstructural modifications (e.g. untempered martensite) that may have resulted.

The active ingredient in Nital formulations, as the name implies, is nitric acid. The nitric acid concentration commonly ranges from 1 to 4% for most Mil-Specs, depending upon whether it is intended for micro-etch or macro-etch capability.

Applicable Specifications: MIL-S-5002, MIL-STD-867, LAO103-020 Goodrich Actuation Systems (formerly TRW Lucas Aerospace): Specification #981-060-016, LGPS 3000. Lockheed Martin: NDTS-9111, 5PTPCG10, LMA-PC010 BombardierIQA Aerospace: MPS 176-14 BoeingAffiliated Organisation Nital Etch Specifications: BAC 5436, DPS4.715, PS21205 VoughtInstitute of Quality A sAircraftsurance Industries: 208-9-100, GP 17 G Gulfstream: GSS19200

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ISO 90 01 INTERNATIONALINTERNATIONAL REGISTERED FIRM ACCREDITATIONACCREDITATION BOARD Certificate No.GB200 21 97 Registration No. 0044/ 1 Solutions For

Industry