Bio-based lignin-acrylamide corrosion inhibitor for water-based mud: Taguchi -RSM optimization, and API-aging validation

Abstract

Corrosion control in water-based mud (WBM) remains essential for protecting drilling equipment and minimizing cost and energy losses during drilling operations. However, many conventional corrosion inhibitors raise concerns related to sustainability and chemical burden, creating a need for effective bio-based alternatives that can function under high-temperature WBM conditions. Here, soda lignin (SL) was polymerized with acrylamide (AA) to produce a lignin–acrylamide composite (LAA) with improved solubility for use as a corrosion inhibitor (CI) additive in WBM. LAA yield was optimized using two complementary statistical approaches, namely the Taguchi method and response surface methodology (RSM) based on a central composite design (CCD). Taguchi analysis ranked the influence of factors as temperature > reaction time > AA ratio > catalyst concentration and predicted a maximum yield of 4.893 g, while CCD–RSM provided refined optimization through ANOVA and predicted a maximum yield of 4.653 g. Both models converged on a consistent optimum region near 90 °C, about 4 h, and AA:SL around 2. The novelty of this study lies in the direct comparison of Taguchi and CCD-RSM optimization coupled with drilling-fluid-relevant validation. The optimized LAA achieved a maximum corrosion inhibition efficiency of 73.5% at 500 ppm in carbon steel weight-loss testing after WBM aging at 90 °C for 16 h under API-type conditions.