To evaluate chemical suppliers' quality control processes, you can follow these steps and standards:

1. Establish Evaluation Criteria: Develop a comprehensive set of evaluation criteria to assess both existing and potential suppliers. This should include metrics related to quality, delivery, cost, and service.

2. Quality Management System Audit: Conduct an audit of the chemical suppliers' quality assurance system based on standards such as ISO 9000 or other relevant quality management standards to ensure that their system is complete and functioning effectively.

3. Product/Service Quality Assessment: Evaluate the chemical suppliers' technical capabilities, quality control systems, and whether their products or services meet your requirements and can be used reliably and consistently.

4. Supplier Audits and Assessments: Perform routine audits to identify potential gaps in the chemical suppliers' ability to meet established standards and provide opportunities for improvement.

5. Establish Communication Channels: Create effective communication channels with suppliers to manage and resolve issues promptly.

6. Non-Conformance Handling and Corrective Actions: Ensure that there is a process for handling non-conforming products and implementing corrective actions to continuously improve quality.

7. Monitoring Sub-Suppliers: Suppliers should collect performance data from their sub-suppliers and use it for performance ranking or scorecards, including metrics such as defect rates and on-time delivery performance.

8. Supplier Selection and Evaluation: Ensure that chemical suppliers adhere to a code of conduct, provide high-quality products, remain cost-competitive, deliver on time, and maintain strong financial support. Validate these commitments during the selection and evaluation process.

9. Supplier System Assessment (SSA): Consider conducting an SSA to evaluate the chemical suppliers' quality management system, documentation, and infrastructure, especially for new suppliers or new facilities of existing suppliers.

10. Early Quality Planning: Suppliers should develop processes necessary for product quality planning and collaborate with the buyer to establish quality objectives and product requirements, as well as to set up processes, documentation, and resources.

11. Quality Evaluation: Assess the chemical suppliers' quality systems, production facilities, and process controls to determine their potential impact on production processes.

By following these steps and standards, you can comprehensively evaluate chemical suppliers's quality control processes, ensuring the quality and efficiency of your supply chain.