Magnesium Alloy Phosphating Film Surface Resistance

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Solution Overview

Problem

Conventional conversion treating methods for magnesium alloys result in high surface resistance, which compromises the electromagnetic shielding of electronic devices and fails to meet the corrosion resistance requirements for applications like mobile phone housings.

Innovation Solution

A multi-step process involving degreasing, acid pickling, surface conditioning, pre-phosphating, and phosphating treatments using specific chemical solutions to form a uniform and dense phosphating film on magnesium alloy workpieces, optimizing surface and corrosion resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional conversion treating method is used, then corrosion resistance is enhanced, but surface resistance becomes too high

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidsurface resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters of the conversion treating solution by adding specific organic additives (sodium dodecyl sulfate and oleic acid diethanolamide) to conventional inorganic salts. This parameter modification enables the formation of a phosphating film with lower surface resistance while maintaining corrosion resistance, directly resolving the technical contradiction between these two properties.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite chemical solution combining inorganic phosphating agents (zinc phosphate, manganese phosphate) with organic surfactants (sodium dodecyl sulfate, oleic acid diethanolamide). This composite approach produces a phosphating film that integrates both corrosion protection and electromagnetic shielding properties, simultaneously achieving low surface resistance and high corrosion resistance.

Inventive Principle:

Principle #40Composite materials

2Strength

If conventional conversion treating method is used, then adhesion of coating layer is enhanced, but electromagnetic shielding becomes poor

Engineering Contradiction:

Improveadhesion of coating layerVSAvoidelectromagnetic shielding

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

By modifying the chemical composition of the conversion treating solution to include specific organic additives alongside inorganic phosphating agents, the patent changes the film formation parameters. This results in a phosphating film with optimized surface resistance (below 0.8 ohm) that provides effective electromagnetic shielding while preserving good coating adhesion through the synergistic action of inorganic and organic components.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If conversion treating method is used to form protective film, then corrosion resistance is improved, but surface resistance reflects poor electromagnetic shielding

Engineering Contradiction:

Improveprotective film formationVSAvoidelectromagnetic shielding

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent develops a composite conversion treating solution containing both inorganic phosphating agents (for protective film formation and corrosion resistance) and organic surfactants (for controlling surface resistance). This composite formulation produces a phosphating film that simultaneously achieves corrosion protection and electromagnetic shielding by lowering surface resistance below 0.8 ohm, resolving the contradiction between protective film quality and electromagnetic shielding performance.

Inventive Principle:

Principle #40Composite materials

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 method achieves better corrosion resistance and lower surface resistance, enhancing the electromagnetic shielding of electronic devices while ensuring the stability and effectiveness of the phosphating film.

Implementation Method 1

placing the magnesium alloy workpiece in a phosphating solution to form a phosphating film on the surface of the magnesium alloy workpiece

Methodology Applied

Scientific EffectPhosphating:

Implementation Method 2

placing the magnesium alloy workpiece in an acid pickling solution to remove oxides, release agent, dirt, and magnesium granules

Methodology Applied

Scientific EffectAcid pickling:

Implementation Method 3

the magnesium alloy workpiece is degreased to remove oil from a surface thereof. Degreasing the surface of the magnesium alloy makes the surface of the magnesium alloy to be hydrophilic

Methodology Applied

Scientific EffectDegreasing:

Data Source

PatentUS9416454B2Method for conversion treating surface of magnesium alloy workpiece

Publication Date: 2016.08.16 FU ZHUN PRECISION INDUSTRY (SHEN ZHEN) CO LTD

AI summary

A method for conversion treating a surface of a magnesium alloy workpiece includes the following steps: providing a magnesium alloy workpiece, degreasing the magnesium alloy workpiece, acid pickling the magnesium alloy workpiece in a first acid pickling treatment step, surface conditioning the magnesium alloy workpiece in a first surface conditioning treatment step, acid pickling the magnesium alloy workpiece in a second acid pickling treatment step, surface conditioning the magnesium alloy workpiece in a second surface conditioning treatment step, pre-phosphating the magnesium alloy workpiece in a pre-phosphating treatment step, and phosphating the magnesium alloy workpiece in a phosphating treatment step to form a phosphating film on the surface of the magnesium alloy workpiece.