Top Grades of Stainless Steel Fasteners Used in Solar Installations: A2-70 vs A4-80

Fasteners in solar photovoltaic (PV) systems play a pivotal role in ensuring long-term mechanical stability, corrosion resistance, and overall performance. Two grades — A2-70 and A4-80 — dominate the solar mounting fasteners market due to their balance of mechanical strength and corrosion protection.

This technical brief by Bait Alnuhas outlines the key differences, applications, and selection criteria between these two stainless steel grades for optimal performance in solar infrastructure.

1. Introduction: Why Material Selection Matters in Solar Structures

Solar PV installations are designed for service lifespans exceeding 25 years, often in high-exposure environments such as deserts, coastal zones, and high-humidity regions. In these conditions, fastener material selection becomes critical — suboptimal grade choices can lead to corrosion, loss of preload, and premature system degradation.

Among stainless steel fasteners, A2-70 and A4-80 are the most commonly specified grades for solar applications due to their mechanical strength and environmental compatibility.

2. Understanding Stainless Steel Fastener Grades

Fastener grades such as A2-70 and A4-80 follow the ISO 3506 standard, which classifies stainless steels used in bolts, nuts, and screws based on chemical composition and mechanical properties.

GradeMaterial TypeTypical Alloy CompositionTensile Strength (MPa)Key PropertyA2-70Austenitic Stainless Steel (Type 304)18% Cr, 8% Ni700 MPaExcellent general corrosion resistanceA4-80Austenitic Stainless Steel (Type 316)16% Cr, 10% Ni, 2–3% Mo800 MPaSuperior pitting & crevice corrosion resistance

3. A2-70 Fasteners — The Workhorse for Standard Solar Projects

A2-70

Technical Characteristics

• Tensile Strength: 700 MPa (ISO 3506-1)

• Yield Strength: Approx. 450 MPa

• Corrosion Resistance: Excellent in neutral and mildly acidic environments

• Temperature Range: Up to 300°C continuous service

• Magnetic Properties: Non-magnetic in annealed condition

Applications

Recommended Applications

• Ground-mounted solar arrays in dry inland regions

• Roof-top solar installations in urban environments

• Non-marine, non-industrial exposure zones

Advantages:

• Cost-effective

• Readily available

• Easy fabrication and threading

Limitations:

• Susceptible to chloride-induced pitting corrosion

• Not ideal for coastal or high-salinity conditions

4. A4-80 Fasteners — The Premium Choice for Coastal and Harsh Environments

A4-80

Technical Characteristics

• Tensile Strength: 800 MPa (ISO 3506-1)

• Yield Strength: Approx. 600 MPa

• Corrosion Resistance: Exceptional — withstands chlorides, acids, and industrial pollutants

• Temperature Range: Up to 400°C continuous service

• Magnetic Properties: Non-magnetic

Applications

Recommended Applications

• Coastal solar farms with salt-laden air exposure

• Desert installations with high temperature fluctuations

• Industrial rooftops near chemical processing zones

Advantages:

• Extended lifespan (25+ years)

• Minimal maintenance requirements

• High mechanical strength and corrosion protection

Limitations:

• Higher cost compared to A2-70

• Slightly lower availability in some regions

5. Comparative Analysis: A2-70 vs A4-80 in Solar Installations

PropertyA2-70 (Type 304)A4-80 (Type 316)Tensile Strength700 MPa800 MPaCorrosion ResistanceGoodExcellent (with Mo addition)Chloride ResistanceModerateHighSuitable for Coastal AreasCost EfficiencyService Life (Solar Applications)15–20 years25+ yearsBest Use CaseInland solar installationsCoastal & industrial solar farms

6. Environmental Application Guide

Selecting the right stainless steel grade depends on your specific environmental conditions:

Inland / Dry Environments

Recommended: A2-70

• Low humidity regions

• Minimal airborne contaminants

• Urban and suburban settings

• Cost-effective solution

Coastal / Marine Environments

Recommended: A4-80

• Salt-laden air exposure

• High humidity conditions

• Offshore installations

• Long-term durability required

Industrial / Chemical Environments

Recommended: A4-80

• Chemical processing areas

• High pollution zones

• Acidic or alkaline atmospheres

• Maximum corrosion resistance needed

7. Bait Alnuhas — Engineering Fastening Reliability for Solar Infrastructure

At Bait Alnuhas, we supply both A2-70 and A4-80 stainless steel fasteners that meet international standards such as ISO 3506, DIN, and ASTM A193/A194.

Quality Testing

Tensile and hardness testing with salt spray (ASTM B117) and humidity chamber tests

Precision Engineering

Dimensional and thread accuracy inspection for perfect fit and performance

Full Traceability

Batch-level traceability and MTC documentation for quality assurance

Expert Guidance

Technical support to select the right material grade for your specific application

Conclusion: Selecting the Right Grade for Long-Term Efficiency

The choice between A2-70 and A4-80 stainless steel fasteners ultimately depends on site conditions, environmental exposure, and budget. While A2-70 provides an economical solution for standard installations, A4-80 delivers superior performance in harsh, saline, or high-moisture zones — ensuring the mechanical integrity and operational reliability of solar assets throughout their design life.

In summary:

• A2-70 = cost-effective reliability for inland sites

• A4-80 = corrosion-proof strength for coastal and industrial environments

For project-specific guidance and grade recommendations, consult Bait Alnuhas — your trusted partner in fastening the foundations of renewable energy.

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Need Expert Guidance for Your Solar Project?

Partner with Bait Alnuhas for the right stainless steel fasteners for your solar installation. Our technical team can help you select the optimal grade based on your environmental conditions and project requirements.

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