When a thin layer of the yellow precious metal is applied to a base of the white precious metal, concerns arise about the long-term appearance of the item. The darkening and discoloration of metallic surfaces, a process caused by reaction with environmental elements, is a key consideration. Specifically, the vulnerability of the underlying metal to sulfur and other reactive substances is a determining factor in the overall durability of the finish.
The selection of fabrication materials for jewelry and decorative objects often involves balancing cost, aesthetics, and longevity. The application of a thin coating can enhance the appearance of a more affordable base material, offering the look of luxury at a reduced price point. However, the potential for the base metal to react and degrade the coating compromises this benefit. This potential degradation, in turn, can diminish the visual appeal and reduce the lifespan of the object, potentially negating the initial cost savings.
The following discussion will address the factors influencing the integrity of gilded surfaces on silver, including environmental considerations, protective measures, and best practices for care and maintenance. Understanding these variables is crucial for preserving the appearance and value of items utilizing this fabrication technique.
1. Base Metal Sensitivity
The inherent reactivity of the underlying metal significantly influences whether gold over silver tarnishes. The degree to which the base metal interacts with environmental elements dictates the rate and extent of any discoloration observed on the surface. The greater the sensitivity of the base metal, the higher the likelihood of tarnishing, even with a protective layer of gold.
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Silver’s Affinity for Sulfur
Silver exhibits a strong chemical affinity for sulfur compounds present in air and moisture. This interaction forms silver sulfide, the black or brown substance commonly recognized as tarnish. When gold plating is thin or porous, sulfur can penetrate and react with the underlying silver, leading to visible discoloration. For example, jewelry worn in environments with high sulfur concentrations, such as industrial areas or near hot springs, is more prone to tarnishing.
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Purity of the Silver Alloy
The composition of the silver alloy used as the base metal affects its susceptibility to tarnishing. Sterling silver, typically composed of 92.5% silver and 7.5% other metals (usually copper), is more prone to tarnishing than fine silver (99.9% silver). Copper reacts with oxygen and can accelerate the tarnishing process. Therefore, a piece made with 925 sterling silver is more likely to show tarnishing under the gold layer than a piece crafted from pure, unalloyed silver.
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Electrochemical Potential
The difference in electrochemical potential between gold and silver can contribute to corrosion. In the presence of an electrolyte (such as moisture), a galvanic cell can form, with silver acting as the anode and gold as the cathode. This process accelerates the oxidation of silver and its subsequent tarnishing. For instance, sweat contains electrolytes that can facilitate this galvanic corrosion, leading to accelerated tarnishing in jewelry worn close to the skin.
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Porosity and Defects in the Gold Layer
Any imperfections in the gold plating, such as pinholes, scratches, or an uneven coating, provide pathways for environmental elements to reach the silver base. These defects create localized areas where tarnishing can initiate and spread. Imagine a gold-plated silver locket with a tiny scratch; tarnish will likely appear first around the scratch, eventually spreading under the gold layer, demonstrating how imperfections exacerbate the effects of base metal sensitivity.
The characteristics of the base metal, especially its inherent reactivity, are critical determinants of whether items utilizing gold over silver will tarnish. Minimizing the base metal’s exposure through thicker, denser plating, barrier layers, or specialized alloys can delay the onset of tarnishing. Understanding these principles informs choices that promote the longevity and aesthetic appeal of these items.
2. Gold Layer Porosity
The presence of pores, microscopic openings, or discontinuities within the gold layer applied over silver directly affects the likelihood of tarnish formation. This porosity allows environmental elements, primarily sulfur compounds, to permeate the gold and reach the underlying silver. The subsequent reaction between silver and sulfur results in the development of silver sulfide, the visible dark tarnish that compromises the aesthetic appeal of the item. A gold layer intended to protect the silver base becomes ineffective when porosity is present, acting as a conduit rather than a barrier. For example, electroplated gold, if applied improperly with insufficient density or inadequate surface preparation, often exhibits significant porosity, leading to rapid tarnishing of the silver underneath.
The degree of porosity is directly related to the application method, the composition of the gold plating solution, and the presence of impurities. Thicker gold layers generally offer better protection, but even relatively thick layers can fail if they contain numerous pores. Techniques such as electroforming or physical vapor deposition (PVD) often produce denser, less porous gold layers compared to traditional electroplating, resulting in superior tarnish resistance. Furthermore, the inclusion of specific alloying elements in the gold plating solution can affect its density and microstructure, thus altering its porosity. Consider two silver bracelets, one plated with electroplated gold and the other with PVD gold. The electroplated bracelet would likely exhibit tarnish far sooner than the PVD-coated one due to the inherent difference in layer density.
In conclusion, gold layer porosity represents a critical vulnerability in gold-over-silver applications. Controlling and minimizing porosity is paramount to achieving lasting tarnish resistance. While complete elimination of porosity is challenging, optimizing plating techniques, material selection, and surface preparation significantly reduces the risk of tarnish. This understanding informs manufacturing processes and maintenance protocols designed to preserve the appearance and value of items constructed with this material combination. Future efforts may focus on developing novel plating methods or incorporating barrier layers to further mitigate the impact of gold layer porosity.
3. Environmental Exposure
Environmental exposure serves as a critical catalyst in the tarnishing process of gold-over-silver items. The surrounding atmosphere, encompassing humidity, pollutants, and temperature fluctuations, directly influences the rate at which silver, even when coated with gold, reacts and discolors. While gold itself is chemically inert under most common conditions, the underlying silver remains susceptible to atmospheric agents if the gold layer is not entirely impermeable. Therefore, the degree and nature of environmental interaction are significant determinants of the long-term appearance of such items. For instance, a gold-plated silver necklace stored in a humid environment with high sulfur dioxide levels will invariably tarnish more rapidly than one kept in a dry, controlled setting. The presence of corrosive substances accelerates the chemical reactions leading to the formation of silver sulfide, the primary component of tarnish.
The impact of environmental exposure is further modulated by the physical characteristics of the gold layer and the composition of the silver alloy. Porous or thin gold plating offers minimal protection, allowing atmospheric elements direct access to the silver substrate. Similarly, the presence of copper in sterling silver alloys increases the susceptibility to corrosion, thereby exacerbating the effects of environmental exposure. Consider the case of antique gold-plated silverware; the degradation of the plating over time, coupled with decades of exposure to varying environmental conditions, often results in extensive tarnishing of the underlying silver, despite the presence of the gold layer. Cleaning and storage practices significantly influence how environmental factors accelerate the tarnishing process. A lack of regular cleaning, or improper storage, allows harmful substances to accumulate and react with the silver, promoting tarnish development.
Understanding the interplay between environmental exposure and gold-over-silver tarnishing is essential for both consumers and manufacturers. Implementing preventative measures, such as employing thicker, denser gold plating, using tarnish-resistant silver alloys, and storing items in controlled environments, mitigates the risk of discoloration. Regular cleaning with appropriate polishing agents further minimizes the accumulation of corrosive substances. Ultimately, recognizing environmental exposure’s critical role in the degradation process enables informed decisions aimed at preserving the aesthetic integrity and longevity of gold-plated silver artifacts. These considerations underscore the inherent challenges in maintaining the appearance of such composite materials over extended periods.
4. Sulfur Compounds
The presence of sulfur compounds in the environment represents a primary cause of tarnish on gold-over-silver items. These compounds, which include hydrogen sulfide (H2S), sulfur dioxide (SO2), and various organic sulfur species, react with silver to form silver sulfide (Ag2S), a black or brownish substance commonly known as tarnish. Even a thin gold layer, if porous or discontinuous, does not prevent the diffusion of sulfur compounds to the underlying silver. The rate and extent of tarnish formation are directly proportional to the concentration of sulfur compounds in the surrounding air and the humidity level, which facilitates the reaction. For example, jewelry stored in a velvet-lined box containing sulfur-treated anti-tarnish strips will still exhibit tarnishing if the gold plating is not sufficiently thick or dense. This demonstrates the potency of sulfur compounds in overcoming the protective barrier of gold.
The impact of sulfur compounds is particularly pronounced in industrial areas or regions with volcanic activity, where their atmospheric concentration is significantly elevated. Similarly, certain household products, such as rubber bands and some cleaning agents, release sulfurous fumes that can accelerate the tarnishing process. The tarnishing of antique gold-plated silverware stored in old wooden chests is often attributable to sulfur compounds released from the wood itself. In response, manufacturers sometimes incorporate barrier layers, such as palladium or nickel, between the gold and silver to impede the diffusion of sulfur. Furthermore, regular cleaning with appropriate tarnish-removing solutions is crucial for mitigating the effects of sulfur compounds. The effectiveness of these solutions depends on their ability to chemically reverse the formation of silver sulfide without damaging the gold plating.
In summary, sulfur compounds constitute a major environmental threat to gold-over-silver items. Understanding their role in the tarnishing process allows for the implementation of preventative measures, including selecting denser plating methods, employing barrier layers, controlling storage conditions, and adopting appropriate cleaning practices. Addressing the challenge posed by sulfur compounds is essential for preserving the aesthetic integrity and extending the lifespan of gold-plated silver objects. The ongoing development of advanced plating techniques and protective coatings aims to further enhance resistance to sulfur-induced tarnishing.
5. Electrolytic Corrosion
Electrolytic corrosion plays a significant role in the tarnishing process of gold-over-silver items. This type of corrosion, also known as galvanic corrosion, occurs when two dissimilar metals, such as gold and silver, are in electrical contact in the presence of an electrolyte, such as moisture or sweat. The electrochemical potential difference between the metals creates a galvanic cell, where the more active metal (silver, in this case) corrodes preferentially while the more noble metal (gold) is protected. As silver corrodes, silver ions are released, which then react with environmental elements, particularly sulfur, to form silver sulfide the visible tarnish. The gold layer, intended as a protective barrier, may accelerate this corrosion if it contains pores or imperfections that allow electrolyte penetration, creating numerous localized corrosion sites. For instance, a gold-plated silver ring worn daily is exposed to sweat containing salts and other electrolytes, which facilitates galvanic corrosion, leading to tarnishing despite the gold plating. Understanding this electrochemical mechanism is crucial in mitigating tarnish in gold-over-silver applications.
The intensity of electrolytic corrosion is influenced by several factors, including the specific composition of the gold and silver alloys, the concentration and type of electrolyte, temperature, and the surface area ratio of the two metals. A larger exposed area of silver relative to the gold plating increases the overall corrosion rate. Additionally, impurities within the gold layer or the silver alloy can create micro-galvanic cells, further accelerating the corrosion process. Consider a scenario involving a gold-plated silver contact in an electronic device operating in a humid environment. The humidity acts as the electrolyte, leading to corrosion of the silver at the interface with the gold. This corrosion not only degrades the silver but also can affect the electrical performance of the contact over time. Applying a conformal coating, a non-conductive protective layer, minimizes the moisture and electrolyte contact, reducing electrolytic corrosion.
In conclusion, electrolytic corrosion is a critical mechanism contributing to the tarnishing of gold-over-silver items. This process, driven by the electrochemical potential difference between the metals in the presence of an electrolyte, leads to the preferential corrosion of silver and subsequent tarnish formation. Minimizing moisture exposure, selecting denser, less porous gold plating techniques, and employing barrier layers between the gold and silver can significantly reduce the effects of electrolytic corrosion. Future research should focus on developing advanced protective coatings and corrosion inhibitors to further enhance the durability and aesthetic appeal of gold-over-silver products. These methods improve product longevity.
6. Barrier Layers
The strategic use of intermediate coatings, termed barrier layers, significantly mitigates tarnishing when gold is applied over silver. These layers act as a physical and chemical buffer, impeding the migration of corrosive substances to the underlying silver and preventing the diffusion of silver ions to the surface. Effective implementation of barrier layers enhances the durability and aesthetic longevity of gold-over-silver items.
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Palladium as a Diffusion Barrier
Palladium, due to its inertness and ability to form a dense, impermeable layer, is frequently employed as a barrier between gold and silver. It effectively blocks the diffusion of sulfur and other corrosive elements, preventing them from reaching the silver substrate and causing tarnish. For example, high-end gold-plated jewelry often utilizes a palladium strike layer to enhance tarnish resistance. In contrast, the absence of a palladium barrier layer in cheaper jewelry leads to quicker tarnishing due to direct contact between the gold and silver.
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Nickel as a Cost-Effective Alternative
Nickel is another metal used as a barrier layer, primarily due to its lower cost compared to palladium. While less effective in preventing diffusion, nickel can still provide a significant improvement in tarnish resistance. However, nickel’s potential to cause allergic reactions limits its use in items that come into direct contact with skin. Consider two gold-plated watch cases: one with a nickel barrier layer and the other without. The watch case with nickel is likely to show less tarnishing over time, but may not be suitable for individuals with nickel allergies.
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Optimizing Layer Thickness
The effectiveness of a barrier layer is directly related to its thickness. A layer that is too thin may be insufficient to prevent diffusion, while an excessively thick layer can introduce stress and adhesion problems. Finding the optimal thickness is crucial for maximizing the barrier’s protective capabilities without compromising the overall integrity of the coating system. For instance, in the context of gold-plated electrical connectors, an insufficient barrier layer thickness can lead to rapid corrosion and signal degradation, while an overly thick layer can increase manufacturing costs without providing significant additional benefit.
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Adhesion Promotion
Barrier layers can also serve to improve the adhesion between the gold and silver. Poor adhesion can lead to delamination, exposing the silver and accelerating tarnishing. Certain barrier metals, such as copper or chromium, can promote adhesion by forming strong metallurgical bonds with both the gold and silver. In the manufacture of gold-plated silver mirrors, an adhesion-promoting barrier layer is essential to prevent the gold from peeling off the silver reflective layer, which would significantly impair the mirror’s performance.
The implementation of barrier layers is a critical strategy in mitigating the tarnishing of gold over silver. The choice of barrier material, its thickness, and its ability to promote adhesion are all important factors that influence the long-term performance of the coating system. The careful selection and application of barrier layers can significantly extend the lifespan and maintain the aesthetic appeal of items constructed with this material combination. The ongoing development of advanced barrier layer materials and deposition techniques aims to further improve their effectiveness in preventing tarnish.
7. Alloy Composition
The specific elemental makeup of both the gold coating and the silver substrate critically influences the tarnishing behavior when the former is layered upon the latter. Subtle variations in these alloys can significantly alter the overall resistance to environmental degradation.
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Copper Content in Sterling Silver
Sterling silver, commonly composed of 92.5% silver and 7.5% copper, exhibits a greater propensity to tarnish compared to pure silver. Copper reacts readily with oxygen and sulfur compounds in the environment, accelerating the formation of silver sulfide (tarnish). If a gold layer is porous or thin, the copper in the underlying sterling silver facilitates tarnish development. For instance, a gold-plated sterling silver spoon tarnishes more quickly than a similar spoon plated over fine silver.
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Alloying Elements in Gold Plating
Gold plating is rarely pure gold; it often contains other metals, such as nickel, cobalt, or copper, to enhance hardness, wear resistance, or color. The presence of these alloying elements can affect the porosity and reactivity of the gold layer. Copper in the gold plating, for instance, can also contribute to tarnish formation by diffusing to the surface and reacting with environmental elements. Consequently, the choice of alloying elements in the gold plating directly impacts the overall tarnish resistance of the gold-over-silver system. A gold alloy containing a higher percentage of copper will tarnish easier.
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Grain Size and Microstructure
The grain size and microstructure of both the gold and silver alloys influence their susceptibility to corrosion. Alloys with smaller grain sizes tend to exhibit higher corrosion resistance due to a larger grain boundary area, which acts as a barrier to diffusion. Similarly, the presence of intermetallic compounds or precipitates within the alloy can affect its electrochemical behavior and corrosion resistance. A gold-plated silver alloy with a refined grain structure shows less susceptibility to tarnish.
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Passivation Layers
Certain alloying elements can promote the formation of passive layers on the surface of the alloy, enhancing its corrosion resistance. Chromium, for example, forms a chromium oxide layer that protects the underlying metal from further oxidation. Incorporating such elements into either the gold or silver alloy can improve the overall tarnish resistance of the gold-over-silver system. A silver alloy with trace amounts of chromium is less likely to tarnish.
In summary, alloy composition plays a pivotal role in determining whether gold over silver tarnishes. The presence of reactive elements like copper, the microstructure of the alloys, and the formation of protective passive layers are all key factors that influence tarnish resistance. Careful selection of alloy compositions is essential for maximizing the durability and aesthetic appeal of items fabricated with this material combination. Variations in alloy components directly influence its long-term appearance and longevity.
8. Maintenance Practices
The enduring visual appeal of gold layered over silver is inextricably linked to consistent and appropriate upkeep. The extent to which proper care is given directly influences the likelihood and rate of tarnish development on such items. Neglecting suitable cleaning and protective measures permits the accumulation of environmental contaminants, thus accelerating the corrosion of the underlying silver through any imperfections in the gold coating. For instance, regularly wiping down gold-plated silverware after use prevents the build-up of food residue and atmospheric pollutants that contribute to tarnish, whereas infrequent cleaning allows these corrosive agents to attack the silver substrate. Correct maintenance is thus not merely an aesthetic concern but an essential factor in preserving the material integrity of the item.
Effective maintenance protocols encompass several key actions. These include regular cleaning with gentle, non-abrasive polishing cloths to remove surface contaminants; appropriate storage in tarnish-resistant bags or boxes to minimize exposure to sulfur compounds and humidity; and avoidance of harsh chemicals or abrasive cleaners that could damage the gold layer. Consider two identical gold-plated necklaces: one cleaned weekly with a specialized jewelry cleaner and stored in a sealed bag, and the other left uncleaned and exposed to the open air. The former will exhibit minimal to no tarnish over an extended period, while the latter will likely show significant discoloration within a shorter timeframe. Furthermore, understanding the specific composition of the gold plating and the silver alloy allows for the selection of cleaning agents that are effective yet non-damaging to the materials.
In summary, diligent maintenance practices are paramount to mitigating the tarnishing of gold over silver. Consistent cleaning, protective storage, and the avoidance of damaging substances collectively contribute to the longevity and aesthetic preservation of these items. The effectiveness of these practices stems from their ability to minimize the exposure of the silver substrate to environmental contaminants and to prevent the build-up of corrosive agents. Recognizing the direct correlation between care routines and material integrity is crucial for both consumers and manufacturers in ensuring that gold-over-silver items retain their value and appearance over time. Without appropriate upkeep, the intrinsic vulnerability of silver to tarnishing will inevitably compromise the intended aesthetic of the gold layering. These factors are considered, it is paramount to understand the care routines needed to protect it.
Frequently Asked Questions About Gold Over Silver Tarnish
This section addresses common inquiries regarding the tarnishing of items constructed with gold layered over silver. The information provided aims to clarify the factors influencing tarnish formation and strategies for its prevention.
Question 1: Does the gold layer itself tarnish when applied over silver?
Pure gold is chemically inert and does not tarnish under normal environmental conditions. However, gold plating often contains alloying elements that can tarnish under specific circumstances. Furthermore, the porosity or thinness of the gold layer allows corrosive elements to reach the silver substrate beneath, leading to silver tarnish that may appear as a discoloration of the entire surface.
Question 2: How quickly does gold over silver tarnish?
The rate of tarnish formation varies significantly based on environmental factors, the thickness and porosity of the gold layer, and the composition of the underlying silver alloy. High humidity, exposure to pollutants, and the presence of copper in the silver accelerate the process. Items exposed to these conditions will tarnish more rapidly.
Question 3: Can tarnishing of gold over silver be prevented entirely?
Complete prevention of tarnishing is difficult, but the process can be significantly slowed. Employing thicker, denser gold plating, using tarnish-resistant silver alloys, storing items in controlled environments, and regularly cleaning with appropriate polishing agents all contribute to minimizing tarnish formation.
Question 4: What are the best cleaning methods for gold-plated silver?
Gentle cleaning with a soft, non-abrasive cloth is recommended. Specialized jewelry cleaning solutions formulated for gold and silver can be used sparingly, following the manufacturer’s instructions carefully. Avoid harsh chemicals or abrasive cleaners, as these can damage the gold layer. Regular, gentle cleaning is preferable to infrequent, aggressive cleaning.
Question 5: Does the karat of the gold plating affect tarnishing?
Higher karat gold plating, being closer to pure gold, is generally more resistant to tarnishing itself. However, the thickness and porosity of the plating are more significant factors. Even high-karat gold plating can allow tarnish to form on the underlying silver if the layer is too thin or contains imperfections.
Question 6: Is tarnishing a sign of poor quality in gold-plated silver items?
Tarnishing, while undesirable, does not automatically indicate poor quality. It is a natural chemical process that occurs over time. However, excessive or rapid tarnishing can be indicative of a thin or porous gold layer, a reactive silver alloy, or inadequate manufacturing processes. Careful inspection of the item and understanding its material composition can provide further insights into its overall quality.
In essence, while gold provides a protective layer to silver, its effectiveness depends on various factors. Regular maintenance and appropriate preventative measures are necessary to preserve the appearance and longevity of items combining these metals.
The subsequent section will detail potential solutions and protective strategies in further detail.
Mitigating Tarnish on Gold Over Silver
The long-term preservation of gold-plated silver items requires proactive measures to combat tarnish. The following guidelines provide actionable strategies for maintaining the aesthetic integrity of such objects.
Tip 1: Select High-Quality Items: Opt for pieces employing thicker gold plating and tarnish-resistant silver alloys, such as those with minimal copper content. Thoroughly inspect items for any visible imperfections in the plating, as these can serve as entry points for corrosive elements.
Tip 2: Implement Proper Storage: Store gold-plated silver in airtight containers or tarnish-resistant bags when not in use. The absence of air exposure reduces the likelihood of sulfur compounds reacting with the silver substrate. Consider including anti-tarnish strips or cloths within the storage container.
Tip 3: Conduct Regular Gentle Cleaning: Employ soft, non-abrasive cloths to wipe down items after each use. This removes surface contaminants like oils, sweat, and dust that can accelerate tarnishing. Avoid using harsh chemicals or abrasive cleaners, as these can damage the gold plating.
Tip 4: Avoid Exposure to Harsh Environments: Refrain from wearing gold-plated silver jewelry during activities that expose it to harsh chemicals, such as swimming in chlorinated pools or cleaning with strong detergents. Direct contact with these substances can compromise the gold layer and promote tarnish.
Tip 5: Consider Barrier Layer Application: For items prone to frequent use or exposure, explore the possibility of applying a protective barrier layer, such as a specialized jewelry sealant. This adds an extra layer of defense against environmental contaminants, however it should not be considered a permanent protection.
Tip 6: Routine Professional Inspection: Implement regular inspection of items. A professional might identify early warning signs of deterioration not observed in an initial cleaning. The professional can offer solutions that prevent tarnish, and ensure your items aesthetic appeal.
Adhering to these recommendations significantly extends the lifespan and maintains the visual appeal of gold-plated silver objects. The careful application of these preventative measures ensures the continued value and beauty of these composite items.
The subsequent section concludes this discourse, summarizing the key findings and underscoring the importance of informed decision-making in managing the tarnishing of gold-over-silver items.
Conclusion
This exploration has confirmed that, indeed, gold over silver tarnish. The inherent properties of silver, particularly its susceptibility to reacting with sulfur compounds, necessitate careful consideration when combining it with a gold coating. The effectiveness of gold as a protective barrier is contingent upon its thickness, density, and freedom from imperfections. Environmental factors, alloy composition, and maintenance practices further contribute to the overall tarnishing process.
The prudent management of these variables remains paramount for preserving the aesthetic value and longevity of items utilizing gold over silver. A thorough understanding of the underlying mechanisms driving tarnish formation is crucial for informed decision-making in material selection, fabrication processes, and care protocols. Ongoing research into advanced protective coatings and innovative alloy compositions offers potential avenues for further mitigating the challenges associated with this material combination.
