Trivalent Chromium Passivation Layer Iron Ion Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing passivation compositions for zinc or zinc-nickel coated substrates often fail to provide superior corrosion resistance and desired color while increasing iron ion concentrations, leading to compromised corrosion protection and frequent replacement, which is costly and environmentally challenging.
Innovation Solution
A passivation composition containing trivalent chromium ions, a complexing agent, and corrosion-inhibiting agents such as unsubstituted or substituted azole compounds or aliphatic organic acids with mercapto-groups, which suppress iron ion release and enhance corrosion protection, achieving a uniform blue or bluish chromium-comprising passivation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional passivation compositions are used, then chromium-comprising passivation layers can be deposited on zinc or zinc-nickel coated substrates, but iron ion concentrations increase leading to compromised corrosion protection and frequent replacement
Solution Approach 1:
The patent introduces corrosion-inhibiting agents (azole compounds or mercapto-containing organic acids) as intermediaries that mediate between the passivation composition and the substrate. These agents preferentially bind to iron ions, preventing them from compromising the passivation layer's corrosion protection properties, thereby allowing the passivation composition to maintain effectiveness despite the presence of iron ion contaminants
Solution Approach 2:
The patent converts the harmful effect of iron ion release into a beneficial outcome by using the corrosion-inhibiting agents to sequester these ions. The iron ions, which would normally degrade performance and require frequent replacement, are instead captured by the inhibitors, extending the composition's service life while maintaining protection quality
2Duration of action of stationary object
If conventional passivation compositions are used, then passivation layers can be formed, but the composition life is short requiring frequent replacement which is costly and environmentally challenging
Solution Approach 1:
The patent changes the chemical parameters of the passivation composition by adding corrosion-inhibiting agents that alter the system's behavior regarding iron ion tolerance. This parameter change allows the composition to maintain stable corrosion protection properties even when iron ion concentrations vary, thereby extending usable composition life without sacrificing protection quality
Solution Approach 2:
The corrosion-inhibiting agents serve as intermediaries that buffer the interaction between iron ions and the passivation layer. By introducing these intermediary substances, the system can tolerate higher iron ion concentrations over extended periods while maintaining consistent corrosion protection, thus resolving the contradiction between extended composition life and maintained protection quality
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 solution significantly extends the life of the passivation composition, maintains excellent corrosion protection, and tolerates high iron ion concentrations without compromising quality, resulting in a sustainable and cost-effective method.
Implementation Method 1
Without applying any current, a chromium (III) hydroxide passivation layer or a p-oxo or p-hydroxo-bridged chromium (III) passivation layer is deposited on the surface of the coated substrate
Implementation Method 2
at least one corrosion-inhibiting agent, which suppresses dissolution of iron from a substrate into the passivation composition
Data Source
AI summary
The present inventions refers to a passivation composition for depositing a chromium-comprising passivation layer on a zinc or zinc-nickel coated substrate, the composition comprising:(i) trivalent chromium ions,(ii) at least one complexing agent for the trivalent chromium ions, being different from the at least one corrosion-inhibiting agent, and(iii) at least one corrosion-inhibiting agent, which is(A) one or more than one substituted azole compound and/or salts thereof, together in a total concentration below 10 mg/L, based on the total volume of the passivation composition, and/or(B) one or more than one unsubstituted or substituted aliphatic organic acid with at least one mercapto-group and/or salts thereof, together in a total concentration in a range from 0.001 mg/L to 100 mg/L, based on the total volume of the passivation composition.