Epoxy Adhesive Phosphatization for Metal Corrosion Resistance

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Solution Overview

Problem

Existing structural adhesives for metal substrates, particularly aluminum, lack sufficient corrosion resistance and adhesive strength when exposed to environmental factors like temperature changes, water, oils, salts, and contaminants, leading to weakened bonds over time.

Innovation Solution

A one-component epoxy-based adhesive composition incorporating a low level of phosphorous element-containing (PEC) additives, which includes a curable epoxy compound, reactive urethane or urea group-containing polymers, and an epoxy curing catalyst, to enhance corrosion resistance and bonding strength without altering the initial properties of the metal or adhesive.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional structural adhesives are used for bonding aluminum substrates, then initial adhesive strength is achieved, but corrosion resistance deteriorates when exposed to environmental factors

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidenvironmental degradation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by incorporating phosphorous-containing compounds into the adhesive formulation before application. These compounds perform in-situ phosphatization of the aluminum substrate surface, creating a protective phosphate layer that prevents corrosion before environmental exposure occurs. This pre-treatment integrated into the adhesive application process resolves the contradiction by establishing corrosion protection in advance.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The phosphorous-containing compounds act as intermediaries between the adhesive and the aluminum substrate. They form a phosphate conversion layer on the aluminum surface that serves as a mediator, improving both adhesion and corrosion resistance. This intermediary layer protects the metal substrate from environmental factors while maintaining bond strength.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If adhesive formulations are modified to improve corrosion resistance, then protective properties increase, but adhesive strength may be compromised

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidadhesive strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent employs parameter changes by carefully controlling the concentration and type of phosphorous-containing compounds in the adhesive formulation. By optimizing these parameters, the formulation achieves both corrosion resistance and adhesive strength. The phosphorous compounds modify the chemical properties of the adhesive system to simultaneously provide protective and bonding functions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The adhesive formulation is a composite material combining epoxy resins, phosphorous-containing compounds, and other additives. This composite structure integrates the protective properties of phosphate layers with the bonding properties of the adhesive matrix, resolving the contradiction between corrosion resistance and adhesive strength.

Inventive Principle:

Principle #40Composite materials

3Reliability

If environmental exposure conditions are severe, then corrosion resistance becomes critical, but bond durability decreases over time

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidbond service life

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The phosphorous-containing compounds provide beforehand cushioning by creating a corrosion-resistant phosphate layer on the aluminum substrate before environmental damage can occur. This protective layer acts as a buffer that cushions the substrate against corrosive attacks during the entire service life, maintaining bond durability under severe conditions.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The adhesive composition significantly increases corrosion resistance and maintains bond strength, with lap shear strength improved by up to 30 times after exposure to accelerated corrosion conditions, and exhibits reduced failure modes, while retaining initial adhesive properties.

Implementation Method 1

the term in situ phosphatization (ISP) is used to describe a process for increasing the corrosion resistance of a coating formulation

Methodology Applied

Scientific EffectPhosphatization: Chemical Bonding

Implementation Method 2

U.S. Pat. No. 5,191,029 describes the use of a phosphorous-containing polymer composition containing water-soluble polyvalent metal compounds

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Data Source

PatentUS11492525B2Adhesive formulation

Publication Date: 2022.11.08 DDP SPECIALTY ELECTRONICS MATERIALS US LLC

AI summary

An adhesive composition including an epoxy-based adhesive polymer and a phosphorous element-containing compound; a process for making the adhesive composition; a process for increasing the corrosion resistance property of the adhesive composition; and a process for bonding a metal substrate with the adhesive composition to increase the corrosion resistance of the substrate by at least 40 percent.