Technical Resource
ASTM G1 — Corrosion Coupon Testing Guide
A practical overview of ASTM G1 standard practices for corrosion coupon preparation, cleaning, and evaluation.
What is ASTM G1?
ASTM G1 (Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens) is the foundational standard for weight loss corrosion coupon testing. It defines procedures for specimen preparation before exposure, chemical and mechanical cleaning after retrieval, and the calculation of corrosion rate from measured weight loss.
Coupon Preparation Before Exposure
Per ASTM G1, coupons must be dimensionally measured, degreased with solvent, surface-finished to a defined grit (typically 120-grit), desiccated, and weighed to 0.1 mg accuracy. Each coupon must be uniquely identified with a stamped serial number. Dimensions and initial weight are recorded for later corrosion rate calculation.
Exposure Period and Installation
Exposure duration depends on expected corrosion rate and monitoring objectives. Typical exposure periods range from 30 to 90 days for active production systems. NACE SP0775 provides guidance on coupon placement: coupons should be oriented in the direction of flow and positioned in the lower quadrant of horizontal pipes to capture the most aggressive corrosion conditions.
Retrieval and Cleaning
After retrieval, coupons are visually inspected and photographed. ASTM G1 Annex A provides chemical cleaning solutions for different metals — for example, Clark solution (HCl + antimony trioxide + stannous chloride) for carbon steel. The cleaning procedure removes corrosion products while minimizing loss of base metal.
Corrosion Rate Calculation
Corrosion rate is calculated from the formula: CR (mm/y) = (8.76 x 10^4 x W) / (A x T x D), where W is weight loss in grams, A is surface area in cm², T is exposure time in hours, and D is metal density in g/cm³. Results are typically reported in mm/year or mils per year (mpy).
How to Order ASTM G1-Compliant Coupons
HovoyPetro supplies corrosion coupons fully prepared per ASTM G1, including precision surface finishing, dimensional measurement, serial number stamping, initial weighing, and VCI packaging. Contact us with your material, dimensions, and quantity requirements for a quotation.
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