Vanconol^®RF Series Recommended Solution for Refinery Corrosion Inhibitors

(Tianjin Hi-Perferal Advanced Materials Co., Ltd.)

Abstract

Petroleum refining systems constitute the core downstream segment of the oil industry, primarily responsible for converting crude oil from upstream operations into qualified products such as gasoline, diesel, and lubricating oils through a series of processing technologies. These systems encompass multiple process units including atmospheric and vacuum distillation, catalytic cracking, hydrocracking/hydrotreating, reforming, coking, desulfurization and denitrification, and sour water stripping. Under high-temperature, high-pressure corrosive media conditions, particularly during delayed coking and hydrocracking processes, these systems are susceptible to H₂S-HCl-H₂O corrosion, leading to wall thinning of equipment and piping, valve sealing failure, and weld cracking, which in turn increases maintenance costs and the risk of unplanned shutdowns. The Vanconol^®RF refinery corrosion inhibitor series achieves high corrosion inhibition efficiency, excellent film-forming capability, and stability under various operating conditions through the efficient adsorption of imidazoline-based primary agents combined with multi-component synergistic formulation design.

This recommended solution aims to provide a detailed introduction to the Vanconol®RF series refinery corrosion inhibitors from the aspects of technical mechanism, performance indicators, application scenarios, field validation, and dosing optimization, offering a compliant, efficient, stable, and implementable integrated solution for corrosion control at low-temperature sections of refining enterprises.

1 Introduction

Corrosion in petroleum refining systems is primarily caused by the hydrolysis of chloride compounds in crude oil (such as NaCl, CaCl₂, and MgCl₂) under high-temperature conditions, which generates hydrochloric acid. This acid then reacts with the metallic components of the equipment, leading to corrosion. Meanwhile, sulfur-induced corrosion acts synergistically with hydrochloric acid corrosion, further attacking the equipment metals. Specifically, hydrogen sulfide first reacts with metallic iron to form a fragile, non-dense ferrous sulfide film. Hydrochloric acid then destroys this film, re-releasing hydrogen sulfide and creating a corrosive cycle. Subsequently, the acid directly attacks the iron, forming water-soluble ferrous chloride and leaving the metal surface continuously exposed to further corrosion.

As trends toward heavier crude feedstocks, higher sulfur content, and higher acidity intensify, petroleum refining units are subjected to prolonged exposure to high-temperature, high-pressure, high-flow, and highly corrosive media. This leads to prominent safety risks such as equipment corrosion perforation and unplanned shutdowns. Equipment and process sections primarily constructed of carbon steel are particularly susceptible to pitting corrosion, uniform corrosion, and under-deposit corrosion. To ensure the safe, stable, long-term, full-capacity, and optimized operation of refining systems, the addition of high-performance corrosion inhibitor products has become one of the most effective solutions.

The Vanconol^® RF series refining corrosion inhibitors are designed in accordance with the Q/SHCG110-2017 and Q/SHCG109-2017 standards. They are suitable for the overhead systems of atmospheric distillation columns, prefractionators, and vacuum distillation columns, as well as for the overhead systems of fractionator and stripper columns in delayed coking units and hydrogenation units operating under low-temperature conditions.

2 Introduction to the Vanconol^® RF Series Refining Corrosion Inhibitors

2.1 Mechanism of Action

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The product is formulated with an imidazoline-based corrosion inhibitor as the core active agent. The nitrogen atoms in the imidazoline ring possess strong lone-pair electrons, enabling the formation of stable coordination bonds with metal atoms. Meanwhile, the long-chain alkyl groups in the molecule form a dense hydrophobic protective layer on the metal surface. This unique molecular structural design imparts enhanced adsorption and film-forming properties, allowing rapid adsorption onto metal surfaces and self-assembly into a high-density protective film that effectively blocks contact between corrosive media and the metal substrate.

The product employs a multi-component synergistic compounding technology, which enhances the density of the inhibitor adsorption film while achieving comprehensive corrosion inhibition through the synergistic action of multiple active components:

Anodic inhibition: The active components of the primary agent form a protective film in the anodic region, inhibiting the anodic dissolution process of the metal.

Cathodic inhibition: Synergistic additives form a sparingly soluble deposition layer in the cathodic region, suppressing the cathodic hydrogen evolution reaction.

Passive film formation: The synergistic action of multiple active components promotes the formation of a stable passive film on the metal surface, significantly enhancing protective durability.

Oxygen reduction inhibition: The incorporation of surfactant components facilitates the uniform spreading of active ingredients across the metal surface, forming a complete coverage layer that effectively suppresses the oxygen reduction process.

2.2 Key Parameters

Table1 Typical parameter information for the Vanconol®RF series of corrosion inhibitors

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Category	Product Model	Appearance	Density (20°C) (kg/m3)	Kinematic Viscosity (40℃) (mm2/s)	Pour Point (℃)	pH Value (10%)	Solubility	Emulsification Tendency
Water-soluble Corrosion Inhibitor	RF-401	Yellow to yellow-brown uniform liquid	1000.9	2.55	<-22	8.6	Miscible with water in any proportion	None
	RF-401N	Yellow uniform liquid	1000.9	9.17	<-30	11.9	Miscible with water in any proportion	None
	RF-401W	Brown uniform liquid	1004.8	41	<-22	6.8	Miscible with water in all proportions	None
	RF-402	Yellow to yellowish-brown transparent uniform liquid	954.6	4.46	<-23	4.9	Miscible with water in all proportions	None
	RF-402W	Brown homogeneous liquid	989.6	≤80	≤-20	8.49	Miscible with water in any ratio	None
Oil-soluble corrosion inhibitor	RF-403	Yellow homogeneous liquid	988.8	10.18	<-30	–	Miscible with straight-run gasoline in any ratio	–
	RF-403W	Brown homogeneous liquid	989.9	39.2	<-30	–	Miscible with straight-run gasoline in any ratio	–

2.3 Typical Application Scenario Performance Description

Table 2 Typical Application Scenario Suitability Description

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Product Model	Typical Application Scenario	Product Application Features
RF-401N	Neutralizing corrosion inhibitor for overhead systems of atmospheric distillation columns, primary distillation columns, and vacuum distillation columns	Rapid film formation, low dosage, high corrosion inhibition efficiency
RF-401	Low-temperature water-soluble corrosion inhibitor for the overhead systems of fractionation columns and stripper columns in delayed coking units and hydrogenation units	Rapid film formation, low dosage, high corrosion inhibition efficiency
RF-401W
RF-402		Dense and robust film formation, low dosage, high corrosion inhibition efficiency
RF-402W
RF-403	Low-temperature oil-soluble corrosion inhibitor for the overhead systems of fractionation columns and stripper columns in delayed coking units and hydrogenation units	Robust film formation, low dosage, high corrosion inhibition efficiency
RF-403W

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Note: The static corrosion inhibition evaluation method for RF-401N follows the standard “Q/SHCG109-2017 Technical Requirements for Neutralizing Corrosion Inhibitors in Crude Distillation Units“, while the evaluation methods for the other corrosion inhibitors follow the standard“Q/SHCG110-2017 Technical Requirements for Low-Temperature Corrosion Inhibitors in Delayed Coking Units and Hydrogenation Units“.

3 Field Application Case Study

Case Background: In a refinery, due to the poor quality of the crude oil, the salt content exceeded the specified limit after electrostatic desalting and dehydration, which subsequently led to excessive HCl concentration during downstream atmospheric and vacuum distillation. The monitored Fe ion concentration exceeded 3 mg/L.

Experimental Selection: The corrosion inhibition performance was evaluated according to the test methods specified in“Q/SHCG110-2017 Technical Requirements for Low-Temperature Corrosion Inhibitors in Delayed Coking Units and Hydrogen Units“, and the corrosion behavior of 20# carbon steel substrate in the field water was observed. The experimental results are as follows:

Test Group	Corrosion Inhibitor Dosage	Iron Ion Concentration (ppm)
Blank	0	1041
RF-401W	100	14
RF-401	100	8
RF-401N	100	2

Performance verification: Initially, RF-401N corrosion inhibitor wascontinuously dosed at300 ppm for5 days, after which the iron ion concentration in the overhead was reduced to below3 mg/L. Continuous monitoring of iron ions was initiated, and no rebound was observed. Subsequently, the dosage was reduced to100 ppm, and the monitored iron ion concentration remained below3 mg/L, with stable equipment operation sustained until the end of the refining campaign.

4 Application Guidelines

Scientific product selection: When selecting a corrosion inhibitor, three key factors should be considered comprehensively: unit type, medium characteristics, and operating conditions, to ensure that the protection solution precisely matches the corrosion risk. During selection,refer toTable2 for matching and selection.

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Cost Control: For users prioritizing cost control, RF-401W, RF-402W, or RF-403W can be selectively applied based on specific operating conditions, ensuring corrosion inhibition performance while further reducing production costs.

Dosing Strategy: Select the appropriate dosage concentration based on the injection point.

Continuous Dosing: Suitable for normal operating conditions to maintain a stable chemical concentration. Recommended concentration: 25-30 ppm, which sustains the integrity of the protective film.

Shock Dosing: Applicable for initial start-up, media switching, or restart after maintenance. An initial high concentration (150-200 ppm) facilitates rapid film formation, followed by transition to continuous dosing for maintenance.

Compatibility with Other Chemicals: This series of corrosion inhibitors should avoid direct mixing with anionic chemicals and strong oxidizing biocides (e.g., sodium hypochlorite). Staggered dosing is recommended, with an interval of no less than 2 hours.

Monitoring and Evaluation: To achieve optimal protective performance, the following methods can be employed for monitoring and dynamically adjusting the inhibitor dosage.

Coupon Method: Install standard corrosion coupons at critical locations in the overhead system. Periodically weigh and calculate the corrosion rate to evaluate the actual protective effectiveness of the inhibitor.

Corrosion Probes: Install electrical resistance (ER) probes or linear polarization resistance (LPR) probes online to monitor corrosion rate changes in real-time. The data serves as a basis for dynamic adjustments.

Online pH/Conductivity Monitoring: Monitor pH changes in the condensate water to indirectly assess corrosion tendency.

Dynamic Adjustment Mechanism: Establish a “Monitor-Assess-Adjust” closed-loop management process based on monitoring data feedback. When the corrosion rate exceeds 0.5 mm/a, increase the dosage concentration by 20-30%. When the coupon surface shows an intact protective film and the corrosion rate is below 0.1 mm/a, the dosage concentration can be appropriately reduced by 10-15%. A systematic evaluation is recommended quarterly to optimize the dosing program according to changes in operating conditions.

5 Compliance Statement

The primary corrosion inhibitor used in this product series, imidazoline, exhibits low toxicity and biodegradability, posing minimal ecological risk and showing no tendency toward long-term bioaccumulation or persistence in the environment. Furthermore, this series contains no OP/NP surfactants, and achieves an optimal balance between high protection performance and ecological requirements, making them a class of environmentally friendly corrosion inhibitors that combine performance with sustainability.

For standard compliance test reports, on-site dosing recommendations, corrosion diagnostics, or sample trials, please do not hesitate to contact us.

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